diff --git a/nimbus/db/aristo/TODO.md b/nimbus/db/aristo/TODO.md
index 8ba6161a7..a35630bf9 100644
--- a/nimbus/db/aristo/TODO.md
+++ b/nimbus/db/aristo/TODO.md
@@ -14,3 +14,5 @@
 	of proof nodes is rather small. Also, a right boundary leaf node is
 	typically cleared. This needs to be re-checked when writing the `proof`
 	function mentioned above.
+
+* `aristo_nearby` also qualifies for a re-write, now
diff --git a/nimbus/db/aristo/aristo_debug.nim b/nimbus/db/aristo/aristo_debug.nim
index 5608c2d32..7924c6256 100644
--- a/nimbus/db/aristo/aristo_debug.nim
+++ b/nimbus/db/aristo/aristo_debug.nim
@@ -559,7 +559,7 @@ proc pp*(
       ): string =
   sTab.ppXTab(db.orDefault)
 
-proc pp*(root: VertexID, leg: Leg; db = AristoDbRef(nil)): string =
+proc pp*(leg: Leg; root: VertexID; db = AristoDbRef(nil)): string =
   let db = db.orDefault()
   result = "(" & leg.wp.vid.ppVid & ","
   block:
@@ -583,7 +583,7 @@ proc pp*(hike: Hike; db = AristoDbRef(nil); indent = 4): string =
   else:
     if hike.legs[0].wp.vid != hike.root:
       result &= "(" & hike.root.ppVid & ")" & pfx
-    result &= hike.legs.mapIt(pp(hike.root, it, db)).join(pfx)
+    result &= hike.legs.mapIt(it.pp(hike.root, db)).join(pfx)
   result &= pfx & "(" & hike.tail.ppPathPfx & ")"
   result &= "]"
 
diff --git a/nimbus/db/aristo/aristo_desc/desc_error.nim b/nimbus/db/aristo/aristo_desc/desc_error.nim
index e52fec7eb..85569e182 100644
--- a/nimbus/db/aristo/aristo_desc/desc_error.nim
+++ b/nimbus/db/aristo/aristo_desc/desc_error.nim
@@ -152,8 +152,10 @@ type
 
 
     # Part/proof node errors
+    PartArgNotInCore
     PartArgNotGenericRoot
     PartArgRootAlreadyUsed
+    PartArgRootAlreadyOnDatabase
     PartChkChangedKeyNotInKeyTab
     PartChkChangedVtxMissing
     PartChkCoreKeyLookupFailed
@@ -188,7 +190,6 @@ type
     PartRlpPayloadException
     PartRootKeysDontMatch
     PartRootVidsDontMatch
-    PartRootAlreadyOnDatabase
     PartVtxSlotWasModified
     PartVtxSlotWasNotModified
 
diff --git a/nimbus/db/aristo/aristo_desc/desc_identifiers.nim b/nimbus/db/aristo/aristo_desc/desc_identifiers.nim
index 613c3761f..b5b87a2ae 100644
--- a/nimbus/db/aristo/aristo_desc/desc_identifiers.nim
+++ b/nimbus/db/aristo/aristo_desc/desc_identifiers.nim
@@ -329,6 +329,11 @@ func to*(n: UInt256; T: type PathID): T =
   ## Representation of a scalar as `PathID` (preserving full information)
   T(pfx: n, length: 64)
 
+func to*(a: PathID; T: type UInt256): T =
+  if not a.pfx.isZero:
+    assert a.length < 64 # debugging only
+    result = a.pfx shr (4 * (64 -  a.length))
+
 # ------------------------------------------------------------------------------
 # Public helpers: Miscellaneous mappings
 # ------------------------------------------------------------------------------
diff --git a/nimbus/db/aristo/aristo_nearby.nim b/nimbus/db/aristo/aristo_nearby.nim
index 9c35674ae..47bf934f1 100644
--- a/nimbus/db/aristo/aristo_nearby.nim
+++ b/nimbus/db/aristo/aristo_nearby.nim
@@ -151,11 +151,11 @@ proc zeroAdjust(
   if 0 < hike.legs.len:
     return ok(hike)
 
-  let root = db.getVtx (hike.root, hike.root)
-  if root.isValid:
+  let rootVtx = db.getVtx (hike.root, hike.root)
+  if rootVtx.isValid:
     block fail:
       var pfx: NibblesBuf
-      case root.vType:
+      case rootVtx.vType:
       of Branch:
         # Find first non-dangling link and assign it
         let nibbleID = block:
@@ -166,18 +166,28 @@ proc zeroAdjust(
             if hike.tail.len == 0:
               break fail
             hike.tail[0].int8
-        let n = root.branchBorderNibble nibbleID
+        let n = rootVtx.branchBorderNibble nibbleID
         if n < 0:
           # Before or after the database range
           return err((hike.root,NearbyBeyondRange))
-        pfx = root.ePfx & NibblesBuf.nibble(n.byte)
+        pfx = rootVtx.ePfx & NibblesBuf.nibble(n.byte)
 
       of Leaf:
-        pfx = root.lPfx
+        pfx = rootVtx.lPfx
         if not hike.accept pfx:
           # Before or after the database range
           return err((hike.root,NearbyBeyondRange))
 
+        # Pathological case: matching `rootVtx` which is a leaf
+        if hike.legs.len == 0 and hike.tail.len == 0:
+          return ok(Hike(
+            root:     hike.root,
+            legs:     @[Leg(
+              nibble: -1,
+              wp:     VidVtxPair(
+                vid:  hike.root,
+                vtx:  rootVtx))]))
+
       var newHike = pfx.toHike(hike.root, db)
       if 0 < newHike.legs.len:
         return ok(newHike)
@@ -268,10 +278,6 @@ proc nearbyNext(
   # Some easy cases
   let hike = ? hike.zeroAdjust(db, doLeast=moveRight)
 
-  # if hike.legs[^1].wp.vtx.vType == Extension:
-  #   let vid = hike.legs[^1].wp.vtx.eVid
-  #   return hike.complete(vid, db, hikeLenMax, doLeast=moveRight)
-
   var
     uHike = hike
     start = true
diff --git a/nimbus/db/aristo/aristo_part.nim b/nimbus/db/aristo/aristo_part.nim
index ec85c5da5..73bac66ff 100644
--- a/nimbus/db/aristo/aristo_part.nim
+++ b/nimbus/db/aristo/aristo_part.nim
@@ -159,6 +159,16 @@ proc partPut*(
   ok()
 
 
+proc partGetSubTree*(ps: PartStateRef; rootHash: Hash256): VertexID =
+  ## For the argument `roothash` retrieve the root vertex ID of a particular
+  ## sub tree from the partial state descriptor argument `ps`. The function
+  ## returns `VertexID(0)` if there is no match.
+  ##
+  for vid in ps.core.keys:
+    if ps[vid].to(Hash256) == rootHash:
+      return vid
+
+
 proc partReRoot*(
     ps: PartStateRef;
     frRoot: VertexID;
@@ -166,9 +176,11 @@ proc partReRoot*(
       ): Result[void,AristoError] =
   ## Realign a generic root vertex (i.e `$2`..`$(LEAST_FREE_VID-1)`) for a
   ## `proof` state to a new root vertex.
-  if frRoot notin ps.core or frRoot == toRoot:
+  if frRoot == toRoot:
     return ok() # nothing to do
 
+  if frRoot notin ps.core:
+    return err(PartArgNotInCore)
   if frRoot < VertexID(2) or LEAST_FREE_VID <= frRoot.ord or
      toRoot < VertexID(2) or LEAST_FREE_VID <= toRoot.ord:
     return err(PartArgNotGenericRoot)
@@ -176,7 +188,7 @@ proc partReRoot*(
   if toRoot in ps.core:
     return err(PartArgRootAlreadyUsed)
   if ps.db.getVtx((toRoot,toRoot)).isValid:
-    return err(PartRootAlreadyOnDatabase)
+    return err(PartArgRootAlreadyOnDatabase)
 
   # Migrate
   for key in ps.byKey.keys:
diff --git a/nimbus/db/aristo/aristo_part/part_debug.nim b/nimbus/db/aristo/aristo_part/part_debug.nim
index a5d6bf6c4..c658e324c 100644
--- a/nimbus/db/aristo/aristo_part/part_debug.nim
+++ b/nimbus/db/aristo/aristo_part/part_debug.nim
@@ -128,7 +128,7 @@ proc pp*(
   let
     pfx0 = indent.toPfx()
     pfx1 = indent.toPfx(1)
-
+    pfx2 = indent.toPfx(2)
   var pfx = ""
   if dbOk:
     result &= pfx & "<db>" & pfx1 & ps.db.pp(
@@ -147,9 +147,10 @@ proc pp*(
     if 0 < len:
       var qfx = ""
       result &= pfx1 & "{"
-      for (vid,vLst) in ps.core.pairs:
+      for vid in ps.core.keys.toSeq.sorted:
+        let vLst = ps.core.getOrDefault vid
         result &= qfx & "(" & vid.pp & ":" & vLst.pp(ps) & ")"
-        qfx = pfx1
+        qfx = pfx2
       result &= "}"
     pfx = pfx0
   if byKeyOk:
diff --git a/nimbus/db/core_db/backend/aristo_db.nim b/nimbus/db/core_db/backend/aristo_db.nim
index 21139429f..719e879cb 100644
--- a/nimbus/db/core_db/backend/aristo_db.nim
+++ b/nimbus/db/core_db/backend/aristo_db.nim
@@ -11,14 +11,16 @@
 {.push raises: [].}
 
 import
+  eth/common,
   ../../aristo as use_ari,
+  ../../aristo/aristo_desc/desc_identifiers,
   ../../aristo/[aristo_init/memory_only, aristo_walk],
   ../../kvt as use_kvt,
   ../../kvt/[kvt_init/memory_only, kvt_walk],
   ../base/[base_config, base_desc, base_helpers]
 
 # ------------------------------------------------------------------------------
-# Public constructor and helper
+# Public constructors
 # ------------------------------------------------------------------------------
 
 proc create*(dbType: CoreDbType; kvt: KvtDbRef; mpt: AristoDbRef): CoreDbRef =
@@ -51,6 +53,41 @@ proc newAristoVoidCoreDbRef*(): CoreDbRef =
     KvtDbRef.init(use_kvt.VoidBackendRef),
     AristoDbRef.init(use_ari.VoidBackendRef))
 
+proc newCtxByKey*(
+    ctx: CoreDbCtxRef;
+    key: Hash256;
+    info: static[string];
+      ): CoreDbRc[CoreDbCtxRef] =
+  const
+    rvid: RootedVertexID = (VertexID(1),VertexID(1))
+  let
+    db = ctx.parent
+
+    # Find `(vid,key)` on transaction stack
+    inx = block:
+      let rc = db.ariApi.call(findTx, ctx.mpt, rvid, key.to(HashKey))
+      if rc.isErr:
+        return err(rc.error.toError info)
+      rc.value
+
+    # Fork MPT descriptor that provides `(vid,key)`
+    newMpt = block:
+      let rc = db.ariApi.call(forkTx, ctx.mpt, inx)
+      if rc.isErr:
+        return err(rc.error.toError info)
+      rc.value
+
+    # Fork KVT descriptor parallel to `newMpt`
+    newKvt = block:
+      let rc = db.kvtApi.call(forkTx, ctx.kvt, inx)
+      if rc.isErr:
+        discard db.ariApi.call(forget, newMpt)
+        return err(rc.error.toError info)
+      rc.value
+
+  # Create new context
+  ok(db.bless CoreDbCtxRef(kvt: newKvt, mpt: newMpt))
+
 # ------------------------------------------------------------------------------
 # End
 # ------------------------------------------------------------------------------
diff --git a/nimbus/db/core_db/backend/aristo_trace.nim b/nimbus/db/core_db/backend/aristo_trace.nim
new file mode 100644
index 000000000..8a9e17f4e
--- /dev/null
+++ b/nimbus/db/core_db/backend/aristo_trace.nim
@@ -0,0 +1,956 @@
+# Nimbus
+# Copyright (c) 2023-2024 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+#    http://www.apache.org/licenses/LICENSE-2.0)
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+#    http://opensource.org/licenses/MIT)
+# at your option. This file may not be copied, modified, or distributed except
+# according to those terms.
+
+##
+## Database Backend Tracer
+## =======================
+##
+
+{.push raises: [].}
+
+import
+  std/[sequtils, tables, typetraits],
+  eth/common,
+  results,
+  ../../aristo as use_aristo,
+  ../../aristo/aristo_desc,
+  ../../kvt as use_kvt,
+  ../../kvt/kvt_desc,
+  ../base/[base_config, base_desc]
+
+const
+  LogJournalMax = 1_000_000
+    ## Maximal size of a journal (organised as LRU)
+
+type
+  TracePfx = enum
+    TrpOops = 0
+    TrpKvt
+    TrpAccounts
+    TrpGeneric
+    TrpStorage
+
+  TraceRequest* = enum
+    TrqOops = 0
+    TrqFind
+    TrqAdd
+    TrqModify
+    TrqDelete
+
+  TraceDataType* = enum
+    TdtOops = 0
+    TdtBlob                       ## Kvt and Aristo
+    TdtError                      ## Kvt and Aristo
+    TdtVoid                       ## Kvt and Aristo
+    TdtAccount                    ## Aristo only
+    TdtBigNum                     ## Aristo only
+    TdtHash                       ## Aristo only
+
+  TraceDataItemRef* = ref object
+    ## Log journal entry
+    pfx*: TracePfx                ## DB storage prefix
+    info*: int                    ## `KvtApiProfNames` or `AristoApiProfNames`
+    req*: TraceRequest            ## Logged action request
+    case kind*: TraceDataType
+    of TdtBlob:
+      blob*: Blob
+    of TdtError:
+      error*: int                 ## `KvtError` or `AristoError`
+    of TdtAccount:
+      account*: AristoAccount
+    of TdtBigNum:
+      bigNum*: UInt256
+    of TdtHash:
+      hash*: Hash256
+    of TdtVoid, TdtOops:
+      discard
+
+  TraceLogInstRef* = ref object
+    ## Logger instance
+    base: TraceRecorderRef
+    level: int
+    truncated: bool
+    journal: KeyedQueue[Blob,TraceDataItemRef]
+
+  TraceRecorderRef* = ref object of RootRef
+    log: seq[TraceLogInstRef]     ## Production stack for log database
+    db: CoreDbRef
+    kvtSave: KvtApiRef             ## Restore `KVT` data
+    ariSave: AristoApiRef          ## Restore `Aristo` data
+
+doAssert LEAST_FREE_VID <= 256 # needed for journal key byte prefix
+
+# ------------------------------------------------------------------------------
+# Private helpers
+# ------------------------------------------------------------------------------
+
+when CoreDbNoisyCaptJournal:
+  import
+    std/strutils,
+    chronicles,
+    stew/byteutils
+
+  func squeezeHex(s: string; ignLen = false): string =
+    result = if s.len < 20: s else: s[0 .. 5] & ".." & s[s.len-8 .. ^1]
+    if not ignLen:
+      let n = (s.len + 1) div 2
+      result &= "[" & (if 0 < n: "#" & $n else: "") & "]"
+
+  func stripZeros(a: string; toExp = false): string =
+    if 0 < a.len:
+      result = a.toLowerAscii.strip(leading=true, trailing=false, chars={'0'})
+      if result.len == 0:
+        result = "0"
+      elif result[^1] == '0' and toExp:
+        var n = 0
+        while result[^1] == '0':
+          let w = result.len
+          result.setLen(w-1)
+          n.inc
+        if n == 1:
+          result &= "0"
+        elif n == 2:
+          result &= "00"
+        elif 2 < n:
+          result &= "↑" & $n
+
+  func `$$`(w: openArray[byte]): string =
+    w.toHex.squeezeHex
+
+  func `$`(w: Blob): string =
+    w.toHex.squeezeHex
+
+  func `$`(w: UInt256): string =
+    "#" & w.toHex.stripZeros.squeezeHex
+
+  func `$`(w: Hash256): string =
+    "£" & w.data.toHex.squeezeHex
+
+  func `$`(w: VertexID): string =
+    if 0 < w.uint64: "$" & w.uint64.toHex.stripZeros else: "$ø"
+
+  func `$`(w: AristoAccount): string =
+    "(" & $w.nonce & "," & $w.balance & "," & $w.codeHash & ")"
+
+  func `$`(ti: TraceDataItemRef): string =
+    result = "(" &
+      (if ti.pfx == TrpKvt: $KvtApiProfNames(ti.info)
+       elif ti.pfx == TrpOops: "<oops>"
+       else: $AristoApiProfNames(ti.info))
+
+    result &= "," & (
+      case ti.req:
+      of TrqOops: "<oops>"
+      of TrqFind: ""
+      of TrqModify: "="
+      of TrqDelete: "-"
+      of TrqAdd: "+")
+
+    result &= (
+      case ti.kind:
+      of TdtOops: "<oops>"
+      of TdtBlob: $ti.blob
+      of TdtBigNum: $ti.bigNum
+      of TdtHash: $ti.hash
+      of TdtVoid: "ø"
+      of TdtError: (if ti.pfx == TrpKvt: $KvtError(ti.error)
+                    elif ti.pfx == TrpOops: "<oops>"
+                    else: $AristoError(ti.error))
+      of TdtAccount: $ti.account)
+
+    result &= ")"
+
+  func toStr(pfx: TracePfx, key: openArray[byte]): string =
+    case pfx:
+    of TrpOops:
+      "<oops>"
+    of TrpKvt:
+      $$(key.toOpenArray(0, key.len - 1))
+    of TrpAccounts:
+      "1:" & $$(key.toOpenArray(0, key.len - 1))
+    of TrpGeneric:
+      $key[0] & ":" & $$(key.toOpenArray(1, key.len - 1))
+    of TrpStorage:
+      "1:" & $$(key.toOpenArray(0, min(31, key.len - 1))) & ":" &
+        (if 32 < key.len: $$(key.toOpenArray(32, key.len - 1)) else: "")
+
+  func `$`(key: openArray[byte]; ti: TraceDataItemRef): string =
+    "(" &
+      TracePfx(key[0]).toStr(key.toOpenArray(1, key.len - 1)) & "," &
+      $ti & ")"
+
+# -------------------------------
+
+template logTxt(info: static[string]): static[string] =
+  "trace " & info
+
+func topLevel(tr: TraceRecorderRef): int =
+  tr.log.len - 1
+
+# --------------------
+
+proc jLogger(
+    tr: TraceRecorderRef;
+    key: openArray[byte];
+    ti: TraceDataItemRef;
+      ) =
+  ## Add or update journal entry. The `tr.pfx` argument indicates the key type:
+  ##
+  ## * `TrpKvt`: followed by KVT key
+  ## * `TrpAccounts`: followed by <account-path>
+  ## * `TrpGeneric`: followed by <root-ID> + <path>
+  ## * `TrpStorage`: followed by <account-path> + <storage-path>
+  ##
+  doAssert ti.pfx != TrpOops
+  let
+    pfx = @[ti.pfx.byte]
+    lRec = tr.log[^1].journal.lruFetch(pfx & @key).valueOr:
+      if LogJournalMax <= tr.log[^1].journal.len:
+        tr.log[^1].truncated = true
+      discard tr.log[^1].journal.lruAppend(pfx & @key, ti, LogJournalMax)
+      return
+  if ti.req != TrqFind:
+    lRec[] = ti[]
+
+proc jLogger(
+    tr: TraceRecorderRef;
+    accPath: Hash256;
+    ti: TraceDataItemRef;
+      ) =
+  tr.jLogger(accPath.data.toSeq, ti)
+
+proc jLogger(
+    tr: TraceRecorderRef;
+    ti: TraceDataItemRef;
+      ) =
+  tr.jLogger(EmptyBlob, ti)
+
+proc jLogger(
+    tr: TraceRecorderRef;
+    root: VertexID;
+    path: openArray[byte];
+    ti: TraceDataItemRef;
+      ) =
+  tr.jLogger(@[root.byte] & @path, ti)
+
+proc jLogger(
+    tr: TraceRecorderRef;
+    root: VertexID;
+    ti: TraceDataItemRef;
+      ) =
+  tr.jLogger(@[root.byte], ti)
+
+proc jLogger(
+    tr: TraceRecorderRef;
+    accPath: Hash256;
+    stoPath: Hash256;
+    ti: TraceDataItemRef;
+      ) =
+  tr.jLogger(accPath.data.toSeq & stoPath.data.toSeq, ti)
+
+# --------------------
+
+func to(w: AristoApiProfNames; T: type TracePfx): T =
+  case w:
+  of AristoApiProfFetchAccountRecordFn,
+     AristoApiProfFetchAccountStateFn,
+     AristoApiProfDeleteAccountRecordFn,
+     AristoApiProfMergeAccountRecordFn:
+    return TrpAccounts
+  of AristoApiProfFetchGenericDataFn,
+     AristoApiProfFetchGenericStateFn,
+     AristoApiProfDeleteGenericDataFn,
+     AristoApiProfDeleteGenericTreeFn,
+     AristoApiProfMergeGenericDataFn:
+    return TrpGeneric
+  of AristoApiProfFetchStorageDataFn,
+     AristoApiProfFetchStorageStateFn,
+     AristoApiProfDeleteStorageDataFn,
+     AristoApiProfDeleteStorageTreeFn,
+     AristoApiProfMergeStorageDataFn:
+    return TrpStorage
+  else:
+    discard
+  raiseAssert "Unsupported AristoApiProfNames: " & $w
+
+func to(w: KvtApiProfNames; T: type TracePfx): T =
+  TrpKvt
+
+# --------------------
+
+func logRecord(
+    info: KvtApiProfNames | AristoApiProfNames;
+    req: TraceRequest;
+    data: openArray[byte];
+      ): TraceDataItemRef =
+  TraceDataItemRef(
+    pfx:  info.to(TracePfx),
+    info: info.ord,
+    req:  req,
+    kind: TdtBlob,
+    blob: @data)
+
+func logRecord(
+    info: KvtApiProfNames | AristoApiProfNames;
+    req: TraceRequest;
+    error: KvtError | AristoError;
+      ): TraceDataItemRef =
+  TraceDataItemRef(
+    pfx:   info.to(TracePfx),
+    info:  info.ord,
+    req:   req,
+    kind:  TdtError,
+    error: error.ord)
+
+func logRecord(
+    info: KvtApiProfNames | AristoApiProfNames;
+    req: TraceRequest;
+      ): TraceDataItemRef =
+  TraceDataItemRef(
+    pfx:  info.to(TracePfx),
+    info: info.ord,
+    req:  req,
+    kind: TdtVoid)
+
+# --------------------
+
+func logRecord(
+    info: AristoApiProfNames;
+    req: TraceRequest;
+    accRec: AristoAccount;
+      ): TraceDataItemRef =
+  TraceDataItemRef(
+    pfx:     info.to(TracePfx),
+    info:    info.ord,
+    req:     req,
+    kind:    TdtAccount,
+    account: accRec)
+
+func logRecord(
+    info: AristoApiProfNames;
+    req: TraceRequest;
+    state: Hash256;
+      ): TraceDataItemRef =
+  TraceDataItemRef(
+    pfx:  info.to(TracePfx),
+    info: info.ord,
+    req:  req,
+    kind: TdtHash,
+    hash: state)
+
+func logRecord(
+    info: AristoApiProfNames;
+    req: TraceRequest;
+    sto: Uint256;
+      ): TraceDataItemRef =
+  TraceDataItemRef(
+    pfx:    info.to(TracePfx),
+    info:   info.ord,
+    req:    req,
+    kind:   TdtBigNum,
+    bigNum: sto)
+
+# ------------------------------------------------------------------------------
+# Private functions
+# ------------------------------------------------------------------------------
+
+proc kvtTraceRecorder(tr: TraceRecorderRef) =
+  let
+    api = tr.db.kvtApi
+    tracerApi = api.dup
+
+  # Set up new production api `tracerApi` and save the old one
+  tr.kvtSave = api
+  tr.db.kvtApi = tracerApi
+
+  # Update production api
+  tracerApi.get =
+    proc(kvt: KvtDbRef; key: openArray[byte]): Result[Blob,KvtError] =
+      const info = KvtApiProfGetFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      let data = api.get(kvt, key).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, key=($$key), error
+        tr.jLogger(key, logRecord(info, TrqFind, error))
+        return err(error) # No way
+
+      tr.jLogger(key, logRecord(info, TrqFind, data))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, key=($$key), data=($$data)
+      ok(data)
+
+  tracerApi.del =
+    proc(kvt: KvtDbRef; key: openArray[byte]): Result[void,KvtError] =
+      const info = KvtApiProfDelFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let tiRec = block:
+        let rc = api.get(kvt, key)
+        if rc.isOk:
+          logRecord(info, TrqDelete, rc.value)
+        elif rc.error == GetNotFound:
+          logRecord(info, TrqDelete)
+        else:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, key=($$key), error=rc.error
+          tr.jLogger(key, logRecord(info, TrqDelete, rc.error))
+          return err(rc.error)
+
+      # Delete from DB
+      api.del(kvt, key).isOkOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, key=($$key), error
+        tr.jLogger(key, logRecord(info, TrqDelete, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(key, tiRec)
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, key=($$key)
+      ok()
+
+  tracerApi.put =
+    proc(kvt: KvtDbRef; key, data: openArray[byte]): Result[void,KvtError] =
+      const info = KvtApiProfPutFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let
+        hasKey = api.hasKey(kvt, key).valueOr:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, key=($$key), error
+          tr.jLogger(key, logRecord(info, TrqAdd, error))
+          return err(error)
+        mode = if hasKey: TrqModify else: TrqAdd
+
+      # Store on DB
+      api.put(kvt, key, data).isOkOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, key=($$key), data=($$data)
+        tr.jLogger(key, logRecord(info, mode, error))
+        return err(error)
+
+      tr.jLogger(key, logRecord(info, mode, data))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, key=($$key), data=($$data)
+      ok()
+
+  assert tr.kvtSave != tr.db.kvtApi
+  assert tr.kvtSave.del != tr.db.kvtApi.del
+  assert tr.kvtSave.hasKey == tr.db.kvtApi.hasKey
+
+
+proc ariTraceRecorder(tr: TraceRecorderRef) =
+  let
+    api = tr.db.ariApi
+    tracerApi = api.dup
+
+  # Set up new production api `tracerApi` and save the old one
+  tr.ariSave = api
+  tr.db.ariApi = tracerApi
+
+  tracerApi.fetchAccountRecord =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+        ): Result[AristoAccount,AristoError] =
+      const info = AristoApiProfFetchAccountRecordFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let accRec = api.fetchAccountRecord(mpt, accPath).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, error
+        tr.jLogger(accPath, logRecord(info, TrqFind, error))
+        return err(error)
+
+      tr.jLogger(accPath, logRecord(info, TrqFind, accRec))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath, accRec
+      ok accRec
+
+  tracerApi.fetchAccountState =
+    proc(mpt: AristoDbRef;
+         updateOk: bool;
+        ): Result[Hash256,AristoError] =
+      const info = AristoApiProfFetchAccountStateFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let state = api.fetchAccountState(mpt, updateOk).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, updateOk, error
+        tr.jLogger logRecord(info, TrqFind, error)
+        return err(error)
+
+      tr.jLogger logRecord(info, TrqFind, state)
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, updateOk, state
+      ok state
+
+  tracerApi.fetchGenericData =
+    proc(mpt: AristoDbRef;
+         root: VertexID;
+         path: openArray[byte];
+        ): Result[Blob,AristoError] =
+      const info = AristoApiProfFetchGenericDataFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let data = api.fetchGenericData(mpt, root, path).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, root, path=($$path), error
+        tr.jLogger(root, path, logRecord(info, TrqFind, error))
+        return err(error)
+
+      tr.jLogger(root, path, logRecord(info, TrqFind, data))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, root, path=($$path), data
+      ok data
+
+  tracerApi.fetchGenericState =
+    proc(mpt: AristoDbRef;
+         root: VertexID;
+         updateOk: bool;
+        ): Result[Hash256,AristoError] =
+      const info = AristoApiProfFetchGenericStateFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let state = api.fetchAccountState(mpt, updateOk).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, root, updateOk, error
+        tr.jLogger(root, logRecord(info, TrqFind, error))
+        return err(error)
+
+      tr.jLogger(root, logRecord(info, TrqFind, state))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, root, updateOk, state
+      ok state
+
+  tracerApi.fetchStorageData =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+         stoPath: Hash256;
+        ): Result[Uint256,AristoError] =
+      const info = AristoApiProfFetchStorageDataFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let stoData = api.fetchStorageData(mpt, accPath, stoPath).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, stoPath, error
+        tr.jLogger(accPath, stoPath, logRecord(info, TrqFind, error))
+        return err(error)
+
+      tr.jLogger(accPath, stoPath, logRecord(info, TrqFind, stoData))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath, stoPath, stoData
+      ok stoData
+
+  tracerApi.fetchStorageState =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+         updateOk: bool;
+        ): Result[Hash256,AristoError] =
+      const info = AristoApiProfFetchStorageStateFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB
+      let state = api.fetchStorageState(mpt, accPath, updateOk).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, updateOk, error
+        tr.jLogger(accPath, logRecord(info, TrqFind, error))
+        return err(error)
+
+      tr.jLogger(accPath, logRecord(info, TrqFind, state))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath, updateOk, state
+      ok state
+
+  tracerApi.deleteAccountRecord =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+        ): Result[void,AristoError] =
+      const info = AristoApiProfDeleteAccountRecordFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let tiRec = block:
+        let rc = api.fetchAccountRecord(mpt, accPath)
+        if rc.isOk:
+          logRecord(info, TrqDelete, rc.value)
+        elif rc.error == FetchPathNotFound:
+          logRecord(info, TrqDelete)
+        else:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, accPath, error=rc.error
+          tr.jLogger(accPath, logRecord(info, TrqDelete, rc.error))
+          return err(rc.error)
+
+      # Delete from DB
+      api.deleteAccountRecord(mpt, accPath).isOkOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, error
+        tr.jLogger(accPath, logRecord(info, TrqDelete, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(accPath, tiRec)
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath
+      ok()
+
+  tracerApi.deleteGenericData =
+    proc(mpt: AristoDbRef;
+         root: VertexID;
+         path: openArray[byte];
+        ): Result[bool,AristoError] =
+      const info = AristoApiProfDeleteGenericDataFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let tiRec = block:
+        let rc = api.fetchGenericData(mpt, root, path)
+        if rc.isOk:
+          logRecord(info, TrqDelete, rc.value)
+        elif rc.error == FetchPathNotFound:
+          logRecord(info, TrqDelete)
+        else:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, root, path=($$path), error=rc.error
+          tr.jLogger(root, path, logRecord(info, TrqDelete, rc.error))
+          return err(rc.error)
+
+      # Delete from DB
+      let emptyTrie = api.deleteGenericData(mpt, root, path).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, root, path=($$path), error
+        tr.jLogger(root, path, logRecord(info, TrqDelete, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(root, path, tiRec)
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, root, path=($$path), emptyTrie
+      ok emptyTrie
+
+  tracerApi.deleteGenericTree =
+    proc(mpt: AristoDbRef;
+         root: VertexID;
+        ): Result[void,AristoError] =
+      const info = AristoApiProfDeleteGenericTreeFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Delete from DB
+      api.deleteGenericTree(mpt, root).isOkOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, root, error
+        tr.jLogger(root, logRecord(info, TrqDelete, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(root, logRecord(info, TrqDelete))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, root
+      ok()
+
+  tracerApi.deleteStorageData =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+         stoPath: Hash256;
+        ): Result[bool,AristoError] =
+      const info = AristoApiProfDeleteStorageDataFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let tiRec = block:
+        let rc = api.fetchStorageData(mpt, accPath, stoPath)
+        if rc.isOk:
+          logRecord(info, TrqDelete, rc.value)
+        elif rc.error == FetchPathNotFound:
+          logRecord(info, TrqDelete)
+        else:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, accPath, stoPath, error=rc.error
+          tr.jLogger(accPath, stoPath, logRecord(info, TrqDelete, rc.error))
+          return err(rc.error)
+
+      let emptyTrie = api.deleteStorageData(mpt, accPath, stoPath).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, stoPath, error
+        tr.jLogger(accPath, stoPath, logRecord(info, TrqDelete, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(accPath, stoPath, tiRec)
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath, stoPath, emptyTrie
+      ok emptyTrie
+
+  tracerApi.deleteStorageTree =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+        ): Result[void,AristoError] =
+      const info = AristoApiProfDeleteStorageTreeFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Delete from DB
+      api.deleteStorageTree(mpt, accPath).isOkOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, error
+        tr.jLogger(accPath, logRecord(info, TrqDelete, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(accPath, logRecord(info, TrqDelete))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath
+      ok()
+
+  tracerApi.mergeAccountRecord =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+         accRec: AristoAccount;
+        ): Result[bool,AristoError] =
+      const info = AristoApiProfMergeAccountRecordFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let
+        hadPath = api.hasPathAccount(mpt, accPath).valueOr:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, accPath, error
+          tr.jLogger(accPath, logRecord(info, TrqAdd, error))
+          return err(error)
+        mode = if hadPath: TrqModify else: TrqAdd
+
+      # Do the merge
+      let updated = api.mergeAccountRecord(mpt, accPath, accRec).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, hadPath, error
+        tr.jLogger(accPath, logRecord(info, mode, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(accPath, logRecord(info, mode, accRec))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath, accRec, hadPath, updated
+      ok updated
+
+  tracerApi.mergeGenericData =
+    proc(mpt: AristoDbRef;
+         root: VertexID;
+         path: openArray[byte];
+         data: openArray[byte];
+        ): Result[bool,AristoError] =
+      const info = AristoApiProfMergeGenericDataFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let
+        hadPath = api.hasPathGeneric(mpt, root, path).valueOr:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, root, path, error
+          tr.jLogger(root, path, logRecord(info, TrqAdd, error))
+          return err(error)
+        mode = if hadPath: TrqModify else: TrqAdd
+
+      # Do the merge
+      let updated = api.mergeGenericData(mpt, root, path, data).valueOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, root, path, error
+        tr.jLogger(root, path, logRecord(info, mode, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(root, path, logRecord(info, mode, data))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, root, path, data=($$data), hadPath, updated
+      ok updated
+
+  tracerApi.mergeStorageData =
+    proc(mpt: AristoDbRef;
+         accPath: Hash256;
+         stoPath: Hash256;
+         stoData: UInt256;
+        ): Result[void,AristoError] =
+      const info = AristoApiProfMergeStorageDataFn
+
+      when CoreDbNoisyCaptJournal:
+        let level = tr.topLevel()
+
+      # Find entry on DB (for comprehensive log record)
+      let
+        hadPath = api.hasPathStorage(mpt, accPath, stoPath).valueOr:
+          when CoreDbNoisyCaptJournal:
+            debug logTxt $info, level, accPath, stoPath, error
+          tr.jLogger(accPath, stoPath, logRecord(info, TrqAdd, error))
+          return err(error)
+        mode = if hadPath: TrqModify else: TrqAdd
+
+      # Do the merge
+      api.mergeStorageData(mpt, accPath, stoPath,stoData).isOkOr:
+        when CoreDbNoisyCaptJournal:
+          debug logTxt $info, level, accPath, stoPath, error
+        tr.jLogger(accPath, stoPath, logRecord(info, mode, error))
+        return err(error)
+
+      # Log on journal
+      tr.jLogger(accPath, stoPath,  logRecord(info, mode, stoData))
+
+      when CoreDbNoisyCaptJournal:
+        debug logTxt $info, level, accPath, stoPath, stoData, hadPath
+      ok()
+
+  assert tr.ariSave != tr.db.ariApi
+  assert tr.ariSave.deleteAccountRecord != tr.db.ariApi.deleteAccountRecord
+  assert tr.ariSave.hasPathAccount == tr.db.ariApi.hasPathAccount
+
+# ------------------------------------------------------------------------------
+# Public functions
+# ------------------------------------------------------------------------------
+
+proc topInst*(tr: TraceRecorderRef): TraceLogInstRef =
+  ## Get top level logger
+  tr.log[^1]
+
+func truncated*(log: TraceLogInstRef): bool =
+  ## True if journal was truncated due to collecting too many entries
+  log.truncated
+
+func level*(log: TraceLogInstRef): int =
+  ## Non-negative stack level of this log instance.
+  log.level
+
+func journal*(log: TraceLogInstRef): KeyedQueue[Blob,TraceDataItemRef] =
+  ## Get the journal
+  log.journal
+
+func db*(log: TraceLogInstRef): CoreDbRef =
+  ## Get database
+  log.base.db
+
+iterator kvtLog*(log: TraceLogInstRef): (Blob,TraceDataItemRef) =
+  ## Extract `Kvt` journal
+  for p in log.journal.nextPairs:
+    let pfx = TracePfx(p.key[0])
+    if pfx == TrpKvt:
+      yield (p.key[1..^1], p.data)
+
+proc kvtLogBlobs*(log: TraceLogInstRef): seq[(Blob,Blob)] =
+  log.kvtLog.toSeq
+     .filterIt(it[1].kind==TdtBlob)
+     .mapIt((it[0],it[1].blob))
+
+iterator ariLog*(log: TraceLogInstRef): (VertexID,Blob,TraceDataItemRef) =
+  ## Extract `Aristo` journal
+  for p in log.journal.nextPairs:
+    let
+      pfx = TracePfx(p.key[0])
+      (root, key) = block:
+        case pfx:
+        of TrpAccounts,TrpStorage:
+          (VertexID(1), p.key[1..^1])
+        of TrpGeneric:
+          (VertexID(p.key[1]), p.key[2..^1])
+        else:
+          continue
+    yield (root, key, p.data)
+
+proc pop*(log: TraceLogInstRef): bool =
+  ## Reduce logger stack by the argument descriptor `log` which must be the
+  ## top entry on the stack. The function returns `true` if the descriptor
+  ## `log` was not the only one on stack and the stack was reduced by the
+  ## top entry. Otherwise nothing is done and `false` returned.
+  ##
+  let tr = log.base
+  doAssert log.level == tr.topLevel()
+  if 1 < tr.log.len: # Always leave one instance on stack
+    tr.log.setLen(tr.log.len - 1)
+    return true
+
+proc push*(tr: TraceRecorderRef) =
+  ## Push overlay logger instance
+  tr.log.add TraceLogInstRef(base: tr, level: tr.log.len)
+
+# ------------------------------------------------------------------------------
+# Public constructor/destructor
+# ------------------------------------------------------------------------------
+
+proc init*(
+    T: type TraceRecorderRef;     # Recorder desc to instantiate
+    db: CoreDbRef;                # Database
+      ): T =
+  ## Constructor, create initial/base tracer descriptor
+  result = T(db: db)
+  result.push()
+  result.kvtTraceRecorder()
+  result.ariTraceRecorder()
+
+proc restore*(tr: TraceRecorderRef) =
+  ## Restore production API.
+  tr.db.kvtApi = tr.kvtSave
+  tr.db.ariApi = tr.ariSave
+  tr[].reset
+
+# ------------------------------------------------------------------------------
+# End
+# ------------------------------------------------------------------------------
+
diff --git a/nimbus/db/core_db/base.nim b/nimbus/db/core_db/base.nim
index 04a40dcd4..7f9dd6d4f 100644
--- a/nimbus/db/core_db/base.nim
+++ b/nimbus/db/core_db/base.nim
@@ -15,6 +15,7 @@ import
   eth/common,
   "../.."/[constants, errors],
   ".."/[kvt, aristo],
+  ./backend/aristo_db,
   ./base/[api_tracking, base_config, base_desc, base_helpers]
 
 export
@@ -44,7 +45,7 @@ when CoreDbEnableProfiling:
     CoreDbFnInx,
     CoreDbProfListRef
 
-when CoreDbEnableCaptJournal and false:
+when CoreDbEnableCaptJournal:
   import
     ./backend/aristo_trace
   type
@@ -69,33 +70,69 @@ proc ctx*(db: CoreDbRef): CoreDbCtxRef =
   ##
   db.defCtx
 
-proc swapCtx*(db: CoreDbRef; ctx: CoreDbCtxRef): CoreDbCtxRef =
-  ## Activate argument context `ctx` as default and return the previously
-  ## active context. This function goes typically together with `forget()`. A
-  ## valid scenario might look like
-  ## ::
-  ##   proc doSomething(db: CoreDbRef; ctx: CoreDbCtxRef) =
-  ##     let saved = db.swapCtx ctx
-  ##     defer: db.swapCtx(saved).forget()
+proc newCtxByKey*(ctx: CoreDbCtxRef; root: Hash256): CoreDbRc[CoreDbCtxRef] =
+  ## Create new context derived from a matching transaction of the currently
+  ## active context. If successful, the resulting context has the following
+  ## properties:
+  ##
+  ## * Transaction level is 1
+  ## * The state of the accounts column is equal to the argument `root`
+  ##
+  ## If successful, the resulting descriptor **must** be manually released
+  ## with `forget()` when it is not used, anymore.
+  ##
+  ## Note:
+  ##   The underlying `Aristo` backend uses lazy hashing so this function
+  ##   might fail simply because there is no computed state when nesting
+  ##   the next transaction. If the previous transaction needs to be found,
+  ##   then it must called like this:
+  ##   ::
+  ##     let db = ..                             # Instantiate CoreDb handle
   ##     ...
+  ##     discard db.ctx.getAccounts.state()      # Compute state hash
+  ##     db.ctx.newTransaction()                 # Enter new transaction
+  ##
+  ##   However, remember that unused hash computations are contle relative
+  ##   to processing time.
+  ##
+  ctx.setTrackNewApi CtxNewCtxByKeyFn
+  result = ctx.newCtxByKey(root, $api)
+  ctx.ifTrackNewApi: debug logTxt, api, elapsed, root=($$root),  result
+
+proc swapCtx*(ctx: CoreDbCtxRef; db: CoreDbRef): CoreDbCtxRef =
+  ## Activate argument context `ctx` as default and return the previously
+  ## active context. This function goes typically together with `forget()`.
+  ## A valid scenario might look like
+  ## ::
+  ##   let db = ..                             # Instantiate CoreDb handle
+  ##   ...
+  ##   let ctx = newCtxByKey(..).expect "ctx"  # Create new context
+  ##   let saved = db.swapCtx ctx              # Swap context dandles
+  ##   defer: db.swapCtx(saved).forget()       # Restore
+  ##   ...
   ##
   doAssert not ctx.isNil
-  db.setTrackNewApi BaseSwapCtxFn
+  assert db.defCtx != ctx # debugging only
+  db.setTrackNewApi CtxSwapCtxFn
+
+  # Swap default context with argument `ctx`
   result = db.defCtx
+  db.defCtx = ctx
 
   # Set read-write access and install
   CoreDbAccRef(ctx).call(reCentre, db.ctx.mpt).isOkOr:
     raiseAssert $api & " failed: " & $error
   CoreDbKvtRef(ctx).call(reCentre, db.ctx.kvt).isOkOr:
     raiseAssert $api & " failed: " & $error
-  db.defCtx = ctx
+  doAssert db.defCtx != result
   db.ifTrackNewApi: debug logTxt, api, elapsed
 
 proc forget*(ctx: CoreDbCtxRef) =
   ## Dispose `ctx` argument context and related columns created with this
-  ## context. This function fails if `ctx` is the default context.
+  ## context. This function throws an exception `ctx` is the default context.
   ##
   ctx.setTrackNewApi CtxForgetFn
+  doAssert ctx !=  ctx.parent.defCtx
   CoreDbAccRef(ctx).call(forget, ctx.mpt).isOkOr:
     raiseAssert $api & ": " & $error
   CoreDbKvtRef(ctx).call(forget, ctx.kvt).isOkOr:
@@ -713,66 +750,54 @@ proc dispose*(tx: CoreDbTxRef) =
 # Public tracer methods
 # ------------------------------------------------------------------------------
 
-when CoreDbEnableCaptJournal and false: # currently disabled
-  proc newCapture*(
-      db: CoreDbRef;
-        ): CoreDbRc[CoreDbCaptRef] =
-    ## Trace constructor providing an overlay on top of the argument database
-    ## `db`. This overlay provides a replacement database handle that can be
-    ## retrieved via `db.recorder()` (which can in turn be ovelayed.) While
-    ## running the overlay stores data in a log-table which can be retrieved
-    ## via `db.logDb()`.
+when CoreDbEnableCaptJournal:
+  proc pushCapture*(db: CoreDbRef): CoreDbCaptRef =
+    ## ..
     ##
-    ## Caveat:
-    ##   The original database argument `db` should not be used while the tracer
-    ##   is active (i.e. exists as overlay). The behaviour for this situation
-    ##   is undefined and depends on the backend implementation of the tracer.
-    ##
-    db.setTrackNewApi BaseNewCaptureFn
-    result = db.methods.newCaptureFn flags
+    db.setTrackNewApi BasePushCaptureFn
+    if db.tracerHook.isNil:
+      db.tracerHook = TraceRecorderRef.init(db)
+    else:
+      TraceRecorderRef(db.tracerHook).push()
+    result = TraceRecorderRef(db.tracerHook).topInst().CoreDbCaptRef
     db.ifTrackNewApi: debug logTxt, api, elapsed, result
 
-  proc recorder*(cpt: CoreDbCaptRef): CoreDbRef =
-    ## Getter, returns a tracer replacement handle to be used as new database.
-    ## It records every action like fetch, store, hasKey, hasPath and delete.
-    ## This descriptor can be superseded by a new overlay tracer (using
-    ## `newCapture()`, again.)
+  proc level*(cpt: CoreDbCaptRef): int =
+    ## Getter, returns the positive number of stacked instances.
     ##
-    ## Caveat:
-    ##   Unless the desriptor `cpt` referes to the top level overlay tracer, the
-    ##   result is undefined and depends on the backend implementation of the
-    ##   tracer.
-    ##
-    cpt.setTrackNewApi CptRecorderFn
-    result = cpt.methods.recorderFn()
-    cpt.ifTrackNewApi: debug logTxt, api, elapsed
+    let log = cpt.distinctBase
+    log.db.setTrackNewApi CptLevelFn
+    result = log.level()
+    log.db.ifTrackNewApi: debug logTxt, api, elapsed, result
 
-  proc logDb*(cp: CoreDbCaptRef): TableRef[Blob,Blob] =
-    ## Getter, returns the logger table for the overlay tracer database.
+  proc kvtLog*(cpt: CoreDbCaptRef): seq[(Blob,Blob)] =
+    ## Getter, returns the `Kvt` logger list for the argument instance.
     ##
-    ## Caveat:
-    ##   Unless the desriptor `cpt` referes to the top level overlay tracer, the
-    ##   result is undefined and depends on the backend implementation of the
-    ##   tracer.
-    ##
-    cp.setTrackNewApi CptLogDbFn
-    result = cp.methods.logDbFn()
-    cp.ifTrackNewApi: debug logTxt, api, elapsed
+    let log = cpt.distinctBase
+    log.db.setTrackNewApi CptKvtLogFn
+    result = log.kvtLogBlobs()
+    log.db.ifTrackNewApi: debug logTxt, api, elapsed
 
-  proc flags*(cp: CoreDbCaptRef):set[CoreDbCaptFlags] =
-    ## Getter
-    ##
-    cp.setTrackNewApi CptFlagsFn
-    result = cp.methods.getFlagsFn()
-    cp.ifTrackNewApi: debug logTxt, api, elapsed, result
-
-  proc forget*(cp: CoreDbCaptRef) =
+  proc pop*(cpt: CoreDbCaptRef) =
     ## Explicitely stop recording the current tracer instance and reset to
     ## previous level.
     ##
-    cp.setTrackNewApi CptForgetFn
-    cp.methods.forgetFn()
-    cp.ifTrackNewApi: debug logTxt, api, elapsed
+    let db = cpt.distinctBase.db
+    db.setTrackNewApi CptPopFn
+    if not cpt.distinctBase.pop():
+      TraceRecorderRef(db.tracerHook).restore()
+      db.tracerHook = TraceRecorderRef(nil)
+    db.ifTrackNewApi: debug logTxt, api, elapsed, cpt
+
+  proc stopCapture*(db: CoreDbRef) =
+    ## Discard capture instances. This function is equivalent to `pop()`-ing
+    ## all instances.
+    ##
+    db.setTrackNewApi CptStopCaptureFn
+    if not db.tracerHook.isNil:
+      TraceRecorderRef(db.tracerHook).restore()
+      db.tracerHook = TraceRecorderRef(nil)
+    db.ifTrackNewApi: debug logTxt, api, elapsed
 
 # ------------------------------------------------------------------------------
 # End
diff --git a/nimbus/db/core_db/base/api_tracking.nim b/nimbus/db/core_db/base/api_tracking.nim
index 9688af529..039f6803b 100644
--- a/nimbus/db/core_db/base/api_tracking.nim
+++ b/nimbus/db/core_db/base/api_tracking.nim
@@ -50,20 +50,21 @@ type
 
     BaseFinishFn        = "finish"
     BaseLevelFn         = "level"
-    BaseNewCaptureFn    = "newCapture"
-    BaseNewCtxFromTxFn  = "ctxFromTx"
+    BasePushCaptureFn   = "pushCapture"
     BaseNewTxFn         = "newTransaction"
     BasePersistentFn    = "persistent"
     BaseStateBlockNumberFn = "stateBlockNumber"
-    BaseSwapCtxFn       = "swapCtx"
 
-    CptLogDbFn          = "cpt/logDb"
-    CptRecorderFn       = "cpt/recorder"
-    CptForgetFn         = "cpt/forget"
+    CptKvtLogFn         = "kvtLog"
+    CptLevelFn          = "level"
+    CptPopFn            = "pop"
+    CptStopCaptureFn    = "stopCapture"
 
     CtxForgetFn         = "ctx/forget"
     CtxGetAccountsFn    = "getAccounts"
     CtxGetGenericFn     = "getGeneric"
+    CtxNewCtxByKeyFn    = "newCtxByKey"
+    CtxSwapCtxFn        = "swapCtx"
 
     KvtDelFn            = "del"
     KvtGetFn            = "get"
diff --git a/nimbus/no-tracer.nim b/nimbus/tracer.nim
similarity index 50%
rename from nimbus/no-tracer.nim
rename to nimbus/tracer.nim
index 7280bac40..440cc511f 100644
--- a/nimbus/no-tracer.nim
+++ b/nimbus/tracer.nim
@@ -8,39 +8,93 @@
 # at your option. This file may not be copied, modified, or distributed except
 # according to those terms.
 
-# TODO: CoreDb module needs to be updated
+{.push raises: [].}
 
 import
   std/[strutils, json],
-  ./common/common,
-  ./db/[core_db, ledger],
-  ./utils/utils,
-  ./evm/tracer/legacy_tracer,
-  ./constants,
-  ./transaction,
-  ./core/executor,
-  ./evm/[state, types],
   nimcrypto/utils as ncrutils,
-  web3/conversions, ./launcher,
   results,
-  ./beacon/web3_eth_conv
+  web3/conversions,
+  ./beacon/web3_eth_conv,
+  ./common/common,
+  ./constants,
+  ./core/executor,
+  ./db/[core_db, ledger],
+  ./evm/[code_bytes, state, types],
+  ./evm/tracer/legacy_tracer,
+  ./launcher,
+  ./transaction,
+  ./utils/utils
 
-proc getParentHeader(self: CoreDbRef, header: BlockHeader): BlockHeader =
-  self.getBlockHeader(header.parentHash)
+when not CoreDbEnableCaptJournal:
+  {.error: "Compiler flag missing for tracer, try -d:dbjapi_enabled".}
 
 type
-  SaveCtxEnv = object
-    db: CoreDbRef
-    ctx: CoreDbCtxRef
+  CaptCtxRef = ref object
+    db: CoreDbRef               # not `nil`
+    root: common.Hash256
+    ctx: CoreDbCtxRef           # not `nil`
+    cpt: CoreDbCaptRef          # not `nil`
+    restore: CoreDbCtxRef       # `nil` unless `ctx` activated
 
-proc newCtx(com: CommonRef; root: eth_types.Hash256): SaveCtxEnv =
-  let ctx = com.db.ctxFromTx(root).valueOr:
-    raiseAssert "setParentCtx: " & $$error
-  SaveCtxEnv(db: com.db, ctx: ctx)
+const
+  senderName = "sender"
+  recipientName = "recipient"
+  minerName = "miner"
+  uncleName = "uncle"
+  internalTxName = "internalTx"
 
-proc setCtx(saveCtx: SaveCtxEnv): SaveCtxEnv =
-  SaveCtxEnv(db: saveCtx.db, ctx: saveCtx.db.swapCtx saveCtx.ctx)
+proc dumpMemoryDB*(node: JsonNode, cpt: CoreDbCaptRef) {.gcsafe.}
+proc toJson*(receipts: seq[Receipt]): JsonNode {.gcsafe.}
 
+# ------------------------------------------------------------------------------
+# Private helpers
+# ------------------------------------------------------------------------------
+
+template safeTracer(info: string; code: untyped) =
+  try:
+    code
+  except CatchableError as e:
+    raiseAssert info & " name=" & $e.name & " msg=" & e.msg
+
+# -------------------
+ 
+proc init(
+    T: type CaptCtxRef;
+    com: CommonRef;
+    root: common.Hash256;
+      ): T
+      {.raises: [CatchableError].} =
+  let ctx = block:
+    let rc = com.db.ctx.newCtxByKey(root)
+    if rc.isErr:
+      raiseAssert "newCptCtx: " & $$rc.error
+    rc.value
+  T(db: com.db, root: root, cpt: com.db.pushCapture(), ctx: ctx)
+
+proc init(
+    T: type CaptCtxRef;
+    com: CommonRef;
+    topHeader: BlockHeader;
+      ): T
+      {.raises: [CatchableError].} =
+  T.init(com, com.db.getBlockHeader(topHeader.parentHash).stateRoot)
+
+proc activate(cc: CaptCtxRef): CaptCtxRef {.discardable.} =
+  ## Install/activate new context `cc.ctx`, old one in `cc.restore`
+  doAssert not cc.isNil
+  doAssert cc.restore.isNil # otherwise activated, already
+  cc.restore = cc.ctx.swapCtx cc.db
+  cc
+
+proc release(cc: CaptCtxRef) =
+  if not cc.restore.isNil:             # switch to original context (if any)
+    let ctx = cc.restore.swapCtx(cc.db)
+    doAssert ctx == cc.ctx
+  cc.ctx.forget()                      # dispose
+  cc.cpt.pop()                         # discard top layer of actions tracer
+
+# -------------------
 
 proc `%`(x: openArray[byte]): JsonNode =
   result = %toHex(x, false)
@@ -57,17 +111,25 @@ proc toJson(receipt: Receipt): JsonNode =
   else:
     result["status"] = %receipt.status
 
-proc dumpReceipts*(chainDB: CoreDbRef, header: BlockHeader): JsonNode =
+proc dumpReceiptsImpl(
+    chainDB: CoreDbRef;
+    header: BlockHeader;
+      ): JsonNode
+      {.raises: [CatchableError].} =
   result = newJArray()
   for receipt in chainDB.getReceipts(header.receiptsRoot):
     result.add receipt.toJson
 
-proc toJson*(receipts: seq[Receipt]): JsonNode =
-  result = newJArray()
-  for receipt in receipts:
-    result.add receipt.toJson
+# ------------------------------------------------------------------------------
+# Private functions
+# ------------------------------------------------------------------------------
 
-proc captureAccount(n: JsonNode, db: LedgerRef, address: EthAddress, name: string) =
+proc captureAccount(
+    n: JsonNode;
+    db: LedgerRef;
+    address: EthAddress;
+    name: string;
+      ) =
   var jaccount = newJObject()
   jaccount["name"] = %name
   jaccount["address"] = %("0x" & $address)
@@ -82,7 +144,7 @@ proc captureAccount(n: JsonNode, db: LedgerRef, address: EthAddress, name: strin
 
   let code = db.getCode(address)
   jaccount["codeHash"] = %("0x" & ($codeHash).toLowerAscii)
-  jaccount["code"] = %("0x" & toHex(code, true))
+  jaccount["code"] = %("0x" & code.bytes.toHex(true))
   jaccount["storageRoot"] = %("0x" & ($storageRoot).toLowerAscii)
 
   var storage = newJObject()
@@ -92,48 +154,26 @@ proc captureAccount(n: JsonNode, db: LedgerRef, address: EthAddress, name: strin
 
   n.add jaccount
 
-proc dumpMemoryDB*(node: JsonNode, db: CoreDbRef) =
-  var n = newJObject()
-  for k, v in db.ctx.getKvt():
-    n[k.toHex(false)] = %v
-  node["state"] = n
 
-proc dumpMemoryDB*(node: JsonNode, kvt: TableRef[common.Blob, common.Blob]) =
-  var n = newJObject()
-  for k, v in kvt:
-    n[k.toHex(false)] = %v
-  node["state"] = n
+proc traceTransactionImpl(
+    com: CommonRef;
+    header: BlockHeader;
+    transactions: openArray[Transaction];
+    txIndex: uint64;
+    tracerFlags: set[TracerFlags] = {};
+      ): JsonNode
+      {.raises: [CatchableError].}=
+  if header.txRoot == EMPTY_ROOT_HASH:
+    return newJNull()
 
-proc dumpMemoryDB*(node: JsonNode, capture: CoreDbCaptRef) =
-  node.dumpMemoryDB capture.logDb
-
-const
-  senderName = "sender"
-  recipientName = "recipient"
-  minerName = "miner"
-  uncleName = "uncle"
-  internalTxName = "internalTx"
-
-proc traceTransaction*(com: CommonRef, header: BlockHeader,
-                       transactions: openArray[Transaction], txIndex: uint64,
-                       tracerFlags: set[TracerFlags] = {}): JsonNode =
   let
-    # we add a memory layer between backend/lower layer db
-    # and capture state db snapshot during transaction execution
-    capture = com.db.newCapture.value
     tracerInst = newLegacyTracer(tracerFlags)
-    captureCom = com.clone(capture.recorder)
-
-    saveCtx = setCtx com.newCtx(com.db.getParentHeader(header).stateRoot)
-    vmState = BaseVMState.new(header, captureCom).valueOr:
-                return newJNull()
+    cc = activate CaptCtxRef.init(com, header)
+    vmState = BaseVMState.new(header, com).valueOr: return newJNull()
     stateDb = vmState.stateDB
 
-  defer:
-    saveCtx.setCtx().ctx.forget()
-    capture.forget()
+  defer: cc.release()
 
-  if header.txRoot == EMPTY_ROOT_HASH: return newJNull()
   doAssert(transactions.calcTxRoot == header.txRoot)
   doAssert(transactions.len != 0)
 
@@ -142,8 +182,7 @@ proc traceTransaction*(com: CommonRef, header: BlockHeader,
     before = newJArray()
     after = newJArray()
     stateDiff = %{"before": before, "after": after}
-    beforeRoot: common.Hash256
-    beforeCtx: SaveCtxEnv
+    stateCtx = CaptCtxRef(nil)
 
   let
     miner = vmState.coinbase()
@@ -159,13 +198,14 @@ proc traceTransaction*(com: CommonRef, header: BlockHeader,
       before.captureAccount(stateDb, miner, minerName)
       stateDb.persist()
       stateDiff["beforeRoot"] = %($stateDb.rootHash)
-      beforeRoot = stateDb.rootHash
-      beforeCtx = com.newCtx beforeRoot
+      discard com.db.ctx.getAccounts.state(updateOk=true) # lazy hashing!
+      stateCtx = CaptCtxRef.init(com, stateDb.rootHash)
 
     let rc = vmState.processTransaction(tx, sender, header)
     gasUsed = if rc.isOk: rc.value else: 0
 
     if idx.uint64 == txIndex:
+      discard com.db.ctx.getAccounts.state(updateOk=true) # lazy hashing!
       after.captureAccount(stateDb, sender, senderName)
       after.captureAccount(stateDb, recipient, recipientName)
       after.captureAccount(stateDb, miner, minerName)
@@ -176,13 +216,12 @@ proc traceTransaction*(com: CommonRef, header: BlockHeader,
 
   # internal transactions:
   let
-    saveCtxBefore = setCtx beforeCtx
-    stateBefore = LedgerRef.init(capture.recorder, beforeRoot)
-  defer:
-    saveCtxBefore.setCtx().ctx.forget()
+    cx = activate stateCtx
+    ldgBefore = LedgerRef.init(com.db, cx.root)
+  defer: cx.release()
 
   for idx, acc in tracedAccountsPairs(tracerInst):
-    before.captureAccount(stateBefore, acc, internalTxName & $idx)
+    before.captureAccount(ldgBefore, acc, internalTxName & $idx)
 
   for idx, acc in tracedAccountsPairs(tracerInst):
     after.captureAccount(stateDb, acc, internalTxName & $idx)
@@ -195,30 +234,34 @@ proc traceTransaction*(com: CommonRef, header: BlockHeader,
 
   # now we dump captured state db
   if TracerFlags.DisableState notin tracerFlags:
-    result.dumpMemoryDB(capture)
+    result.dumpMemoryDB(cx.cpt)
 
-proc dumpBlockState*(com: CommonRef, blk: EthBlock, dumpState = false): JsonNode =
+
+proc dumpBlockStateImpl(
+    com: CommonRef;
+    blk: EthBlock;
+    dumpState = false;
+      ): JsonNode
+      {.raises: [CatchableError].} =
   template header: BlockHeader = blk.header
+
   let
-    parent = com.db.getParentHeader(header)
-    capture = com.db.newCapture.value
-    captureCom = com.clone(capture.recorder)
-    # we only need a stack dump when scanning for internal transaction address
+    cc = activate CaptCtxRef.init(com, header)
+    parent = com.db.getBlockHeader(header.parentHash)
+
+    # only need a stack dump when scanning for internal transaction address
     captureFlags = {DisableMemory, DisableStorage, EnableAccount}
     tracerInst = newLegacyTracer(captureFlags)
-
-    saveCtx = setCtx com.newCtx(parent.stateRoot)
-    vmState = BaseVMState.new(header, captureCom, tracerInst).valueOr:
-                return newJNull()
+    vmState = BaseVMState.new(header, com, tracerInst).valueOr:
+      return newJNull()
     miner = vmState.coinbase()
-  defer:
-    saveCtx.setCtx().ctx.forget()
-    capture.forget()
+
+  defer: cc.release()
 
   var
     before = newJArray()
     after = newJArray()
-    stateBefore = LedgerRef.init(capture.recorder, parent.stateRoot)
+    stateBefore = LedgerRef.init(com.db, parent.stateRoot)
 
   for idx, tx in blk.transactions:
     let sender = tx.getSender
@@ -259,22 +302,24 @@ proc dumpBlockState*(com: CommonRef, blk: EthBlock, dumpState = false): JsonNode
   result = %{"before": before, "after": after}
 
   if dumpState:
-    result.dumpMemoryDB(capture)
+    result.dumpMemoryDB(cc.cpt)
 
-proc traceBlock*(com: CommonRef, blk: EthBlock, tracerFlags: set[TracerFlags] = {}): JsonNode =
+
+proc traceBlockImpl(
+    com: CommonRef;
+    blk: EthBlock;
+    tracerFlags: set[TracerFlags] = {};
+      ): JsonNode
+      {.raises: [CatchableError].} =
   template header: BlockHeader = blk.header
+
   let
-    capture = com.db.newCapture.value
-    captureCom = com.clone(capture.recorder)
+    cc = activate CaptCtxRef.init(com, header)
     tracerInst = newLegacyTracer(tracerFlags)
+    vmState = BaseVMState.new(header, com, tracerInst).valueOr:
+      return newJNull()
 
-    saveCtx = setCtx com.newCtx(com.db.getParentHeader(header).stateRoot)
-    vmState = BaseVMState.new(header, captureCom, tracerInst).valueOr:
-                return newJNull()
-
-  defer:
-    saveCtx.setCtx().ctx.forget()
-    capture.forget()
+  defer: cc.release()
 
   if header.txRoot == EMPTY_ROOT_HASH: return newJNull()
   doAssert(blk.transactions.calcTxRoot == header.txRoot)
@@ -293,24 +338,33 @@ proc traceBlock*(com: CommonRef, blk: EthBlock, tracerFlags: set[TracerFlags] =
   result["gas"] = %gasUsed
 
   if TracerFlags.DisableState notin tracerFlags:
-    result.dumpMemoryDB(capture)
+    result.dumpMemoryDB(cc.cpt)
 
-proc traceTransactions*(com: CommonRef, header: BlockHeader, transactions: openArray[Transaction]): JsonNode =
+proc traceTransactionsImpl(
+    com: CommonRef;
+    header: BlockHeader;
+    transactions: openArray[Transaction];
+      ): JsonNode
+      {.raises: [CatchableError].} =
   result = newJArray()
   for i in 0 ..< transactions.len:
-    result.add traceTransaction(com, header, transactions, i.uint64, {DisableState})
+    result.add traceTransactionImpl(
+      com, header, transactions, i.uint64, {DisableState})
 
 
-proc dumpDebuggingMetaData*(vmState: BaseVMState, blk: EthBlock, launchDebugger = true) =
+proc dumpDebuggingMetaDataImpl(
+    vmState: BaseVMState;
+    blk: EthBlock;
+    launchDebugger = true;
+      ) {.raises: [CatchableError].} =
   template header: BlockHeader = blk.header
+
   let
-    com = vmState.com
+    cc = activate CaptCtxRef.init(vmState.com, header)
     blockNumber = header.number
-    capture = com.db.newCapture.value
-    captureCom = com.clone(capture.recorder)
     bloom = createBloom(vmState.receipts)
-  defer:
-    capture.forget()
+
+  defer: cc.release()
 
   let blockSummary = %{
     "receiptsRoot": %("0x" & toHex(calcReceiptsRoot(vmState.receipts).data)),
@@ -320,17 +374,82 @@ proc dumpDebuggingMetaData*(vmState: BaseVMState, blk: EthBlock, launchDebugger
 
   var metaData = %{
     "blockNumber": %blockNumber.toHex,
-    "txTraces": traceTransactions(captureCom, header, blk.transactions),
-    "stateDump": dumpBlockState(captureCom, blk),
-    "blockTrace": traceBlock(captureCom, blk, {DisableState}),
+    "txTraces": traceTransactionsImpl(vmState.com, header, blk.transactions),
+    "stateDump": dumpBlockStateImpl(vmState.com, blk),
+    "blockTrace": traceBlockImpl(vmState.com, blk, {DisableState}),
     "receipts": toJson(vmState.receipts),
     "block": blockSummary
   }
 
-  metaData.dumpMemoryDB(capture)
+  metaData.dumpMemoryDB(cc.cpt)
 
   let jsonFileName = "debug" & $blockNumber & ".json"
   if launchDebugger:
     launchPremix(jsonFileName, metaData)
   else:
     writeFile(jsonFileName, metaData.pretty())
+
+# ------------------------------------------------------------------------------
+# Public functions
+# ------------------------------------------------------------------------------
+
+proc traceBlock*(
+    com: CommonRef;
+    blk: EthBlock;
+    tracerFlags: set[TracerFlags] = {};
+      ): JsonNode =
+  "traceBlock".safeTracer:
+    result = com.traceBlockImpl(blk, tracerFlags)
+
+proc toJson*(receipts: seq[Receipt]): JsonNode =
+  result = newJArray()
+  for receipt in receipts:
+    result.add receipt.toJson
+
+proc dumpMemoryDB*(node: JsonNode, cpt: CoreDbCaptRef) =
+  var n = newJObject()
+  for (k,v) in cpt.kvtLog:
+    n[k.toHex(false)] = %v
+  node["state"] = n
+
+proc dumpReceipts*(chainDB: CoreDbRef, header: BlockHeader): JsonNode =
+  "dumpReceipts".safeTracer:
+    result = chainDB.dumpReceiptsImpl header
+
+proc traceTransaction*(
+    com: CommonRef;
+    header: BlockHeader;
+    txs: openArray[Transaction];
+    txIndex: uint64;
+    tracerFlags: set[TracerFlags] = {};
+      ): JsonNode =
+  "traceTransaction".safeTracer:
+      result = com.traceTransactionImpl(header, txs, txIndex,tracerFlags)
+
+proc dumpBlockState*(
+    com: CommonRef;
+    blk: EthBlock;
+    dumpState = false;
+      ): JsonNode =
+  "dumpBlockState".safeTracer:
+    result = com.dumpBlockStateImpl(blk, dumpState)
+
+proc traceTransactions*(
+    com: CommonRef;
+    header: BlockHeader;
+    transactions: openArray[Transaction];
+      ): JsonNode =
+  "traceTransactions".safeTracer:
+    result = com.traceTransactionsImpl(header, transactions)
+
+proc dumpDebuggingMetaData*(
+    vmState: BaseVMState;
+    blk: EthBlock;
+    launchDebugger = true;
+      ) =
+  "dumpDebuggingMetaData".safeTracer:
+    vmState.dumpDebuggingMetaDataImpl(blk, launchDebugger)
+
+# ------------------------------------------------------------------------------
+# End
+# ------------------------------------------------------------------------------
diff --git a/tests/all_tests.nim b/tests/all_tests.nim
index 960ee06d6..c7e93a788 100644
--- a/tests/all_tests.nim
+++ b/tests/all_tests.nim
@@ -16,7 +16,7 @@ cliBuilder:
           ./test_genesis,
           ./test_precompiles,
           ./test_generalstate_json,
-          #./test_tracer_json,                     -- temporarily disabled
+          ./test_tracer_json,
           #./test_persistblock_json,               -- fails
           #./test_rpc,                             -- fails
           ./test_filters,
diff --git a/tests/replay/pp.nim b/tests/replay/pp.nim
index 4e7fedc7f..79a8f6294 100644
--- a/tests/replay/pp.nim
+++ b/tests/replay/pp.nim
@@ -66,7 +66,7 @@ func pp*(h: BlockHeader; sep = " "): string =
     &"receiptsRoot={h.receiptsRoot.pp}{sep}" &
     &"stateRoot={h.stateRoot.pp}{sep}" &
     &"baseFee={h.baseFeePerGas}{sep}" &
-    &"withdrawalsRoot={h.withdrawalsRoot.get(EMPTY_ROOT_HASH)}{sep}" &
+    &"withdrawalsRoot={h.withdrawalsRoot.get(EMPTY_ROOT_HASH).pp}{sep}" &
     &"blobGasUsed={h.blobGasUsed.get(0'u64)}{sep}" &
     &"excessBlobGas={h.excessBlobGas.get(0'u64)}"
 
diff --git a/tests/test_tracer_json.nim b/tests/test_tracer_json.nim
index afe95cb1d..975d0059e 100644
--- a/tests/test_tracer_json.nim
+++ b/tests/test_tracer_json.nim
@@ -9,16 +9,16 @@
 # or distributed except according to those terms.
 
 import
-  std/[json, os, sets, tables, strutils],
+  std/[json, os, tables, strutils],
   stew/byteutils,
   chronicles,
   unittest2,
   results,
   ./test_helpers,
-  ../nimbus/sync/protocol/snap/snap_types,
-  ../nimbus/db/aristo/aristo_merge,
-  ../nimbus/db/kvt/kvt_utils,
   ../nimbus/db/aristo,
+  ../nimbus/db/aristo/[aristo_desc, aristo_layers, aristo_nearby, aristo_part],
+  ../nimbus/db/aristo/aristo_part/part_debug,
+  ../nimbus/db/kvt/kvt_utils,
   ../nimbus/[tracer, evm/types],
   ../nimbus/common/common
 
@@ -28,14 +28,17 @@ proc setErrorLevel {.used.} =
 
 proc preLoadAristoDb(cdb: CoreDbRef; jKvp: JsonNode; num: BlockNumber) =
   ## Hack for `Aristo` pre-lading using the `snap` protocol proof-loader
+  const
+    info = "preLoadAristoDb"
   var
-    proof: seq[SnapProof] # for pre-loading MPT
-    predRoot: Hash256     # from predecessor header
-    txRoot: Hash256       # header with block number `num`
-    rcptRoot: Hash256     # ditto
+    proof: seq[Blob]            # for pre-loading MPT
+    predRoot: Hash256           # from predecessor header
+    txRoot: Hash256             # header with block number `num`
+    rcptRoot: Hash256           # ditto
   let
-    adb = cdb.mpt
-    kdb = cdb.kvt
+    adb = cdb.ctx.mpt           # `Aristo` db
+    kdb = cdb.ctx.kvt           # `Kvt` db
+    ps = PartStateRef.init adb  # Partial DB descriptor
 
   # Fill KVT and collect `proof` data
   for (k,v) in jKvp.pairs:
@@ -45,7 +48,7 @@ proc preLoadAristoDb(cdb: CoreDbRef; jKvp: JsonNode; num: BlockNumber) =
     if key.len == 32:
       doAssert key == val.keccakHash.data
       if val != @[0x80u8]: # Exclude empty item
-        proof.add SnapProof(val)
+        proof.add val
     else:
       if key[0] == 0:
         try:
@@ -60,19 +63,62 @@ proc preLoadAristoDb(cdb: CoreDbRef; jKvp: JsonNode; num: BlockNumber) =
           discard
       check kdb.put(key, val).isOk
 
-  # TODO: `getColumn(CtXyy)` does not exists anymore. There is only the generic
-  #       `MPT` left that can be retrieved with `getGeneric()`, optionally with
-  #       argument `clearData=true`
-
-  # Install sub-trie roots onto production db
-  if txRoot.isValid:
-    doAssert adb.mergeProof(txRoot, VertexID(CtTxs)).isOk
-  if rcptRoot.isValid:
-    doAssert adb.mergeProof(rcptRoot, VertexID(CtReceipts)).isOk
-  doAssert adb.mergeProof(predRoot, VertexID(CtAccounts)).isOk
-
   # Set up production MPT
-  doAssert adb.mergeProof(proof).isOk
+  ps.partPut(proof, AutomaticPayload).isOkOr:
+    raiseAssert info & ": partPut => " & $error
+
+  # Handle transaction sub-tree
+  if txRoot.isValid:
+    var txs: seq[Transaction]
+    for (key,pyl) in adb.rightPairs LeafTie(root: ps.partGetSubTree txRoot):
+      let
+        inx = key.path.to(UInt256).truncate(uint)
+        tx = rlp.decode(pyl.rawBlob, Transaction)
+      #
+      # FIXME: Is this might be a bug in the test data?
+      #
+      #        The single item test key is always `128`. For non-single test
+      #        lists, the keys are `1`,`2`, ..,`N`, `128` (some single digit
+      #        number `N`.)
+      #
+      #        Unless the `128` item value is put at the start of the argument
+      #        list `txs[]` for `persistTransactions()`, the `tracer` module
+      #        will throw an exception at
+      #        `doAssert(transactions.calcTxRoot == header.txRoot)` in the
+      #        function `traceTransactionImpl()`.
+      #
+      if (inx and 0x80) != 0:
+        txs = @[tx] & txs
+      else:
+        txs.add tx
+    cdb.persistTransactions(num, txRoot, txs)
+
+  # Handle receipts sub-tree
+  if rcptRoot.isValid:
+    var rcpts: seq[Receipt]
+    for (key,pyl) in adb.rightPairs LeafTie(root: ps.partGetSubTree rcptRoot):
+      let
+        inx = key.path.to(UInt256).truncate(uint)
+        rcpt = rlp.decode(pyl.rawBlob, Receipt)
+      # FIXME: See comment at `txRoot` section.
+      if (inx and 0x80) != 0:
+        rcpts = @[rcpt] & rcpts
+      else:
+        rcpts.add rcpt
+    cdb.persistReceipts(rcptRoot, rcpts)
+
+  # Save keys to database
+  for (rvid,key) in ps.vkPairs:
+    adb.layersPutKey(rvid, key)
+
+  ps.check().isOkOr:
+    raiseAssert info & ": check => " & $error
+
+  #echo ">>> preLoadAristoDb (9)",
+  #  "\n    ps\n    ", ps.pp(byKeyOk=false,byVidOk=false),
+  #  ""
+  # -----------
+  #if true: quit()
 
 # use tracerTestGen.nim to generate additional test data
 proc testFixtureImpl(node: JsonNode, testStatusIMPL: var TestStatus, memoryDB: CoreDbRef) =
@@ -98,15 +144,25 @@ proc testFixtureImpl(node: JsonNode, testStatusIMPL: var TestStatus, memoryDB: C
   let stateDump = dumpBlockState(com, blk)
   let blockTrace = traceBlock(com, blk, {DisableState})
 
+  # Fix hex representation
+  for inx in 0 ..< node["txTraces"].len:
+    for key in ["beforeRoot", "afterRoot"]:
+      # Here, `node["txTraces"]` stores a string while `txTraces` uses a
+      # `Hash256` which might expand to a didfferent upper/lower case.
+      var strHash = txTraces[inx]["stateDiff"][key].getStr.toUpperAscii
+      if strHash.len < 64:
+        strHash = '0'.repeat(64 - strHash.len) & strHash
+      txTraces[inx]["stateDiff"][key] = %(strHash)
+
   check node["txTraces"] == txTraces
   check node["stateDump"] == stateDump
   check node["blockTrace"] == blockTrace
+
   for i in 0 ..< receipts.len:
     let receipt = receipts[i]
     let stateDiff = txTraces[i]["stateDiff"]
     check receipt["root"].getStr().toLowerAscii() == stateDiff["afterRoot"].getStr().toLowerAscii()
 
-
 proc testFixtureAristo(node: JsonNode, testStatusIMPL: var TestStatus) =
   node.testFixtureImpl(testStatusIMPL, newCoreDbRef AristoDbMemory)