diff --git a/datastore.nimble b/datastore.nimble
index 6252c6d..f3414a6 100644
--- a/datastore.nimble
+++ b/datastore.nimble
@@ -9,7 +9,7 @@ license       = "Apache License 2.0 or MIT"
 requires "nim >= 1.2.0",
          "asynctest >= 0.3.1 & < 0.4.0",
          "chronos",
-         "questionable >= 0.10.3 & < 0.11.0",
+         "questionable >= 0.10.4 & < 0.11.0",
          "sqlite3_abi",
          "stew",
          "unittest2",
diff --git a/datastore/filesystem_datastore.nim b/datastore/filesystem_datastore.nim
index 51c50a0..9ae9a55 100644
--- a/datastore/filesystem_datastore.nim
+++ b/datastore/filesystem_datastore.nim
@@ -3,7 +3,6 @@ import std/os
 import pkg/chronos
 import pkg/questionable
 import pkg/questionable/results
-from pkg/stew/results as stewResults import get, isErr
 import pkg/upraises
 
 import ./datastore
@@ -96,11 +95,11 @@ method get*(
 
   let
     path = self.path(key)
-    containsRes = await self.contains(key)
 
-  if containsRes.isErr: return failure containsRes.error.msg
+  without contain =? await self.contains(key), error:
+    return failure error
 
-  if containsRes.get:
+  if contain:
     var
       file: File
 
diff --git a/datastore/key.nim b/datastore/key.nim
index 1cd32e0..adfef9f 100644
--- a/datastore/key.nim
+++ b/datastore/key.nim
@@ -6,7 +6,10 @@ import std/strutils
 
 import pkg/questionable
 import pkg/questionable/results
+
+# could be removed if problems with questionable are resolved
 from pkg/stew/results as stewResults import get, isErr
+
 import pkg/upraises
 
 export hashes
@@ -156,6 +159,21 @@ proc init*(
       nss: seq[Namespace]
 
     for s in namespaces:
+      # if `, error` is used instead of `, err` then compilation fails with:
+      # Error: cannot use symbol of kind 'func' as a 'template'
+      # maybe related to `from pkg/stew/results as stewResults` at top of module,
+      # which could be removed if other problems with questionable are resolved
+
+      # but when using `, err` then compilation fails with:
+      # SIGSEGV: Illegal storage access
+
+      # but strangely the last call in the stack trace pertains to L211 below
+
+      # without ns =? Namespace.init(s), err:
+      #   return failure "namespaces contains an invalid Namespace: " & err.msg
+      #
+      # nss.add ns
+
       let
         nsRes = Namespace.init(s)
 
@@ -184,14 +202,15 @@ proc init*(
     return failure "id string must not contain only one or more separator " &
       "\"" & separator & "\""
 
-  let
-    keyRes = Key.init(nsStrs)
-
-  if keyRes.isErr:
+  # if `, error` is used instead of `, err` then compilation fails with:
+  # Error: cannot use symbol of kind 'func' as a 'template'
+  # maybe related to `from pkg/stew/results as stewResults` at top of module,
+  # which could be removed if other problems with questionable are resolved
+  without key =? Key.init(nsStrs), err:
     return failure "id string contains an invalid Namespace:" &
-      keyRes.error.msg.split(":")[1..^1].join("").replace("\"\"", "\":\"")
+      err.msg.split(":")[1..^1].join("").replace("\"\"", "\":\"")
 
-  keyRes
+  success key
 
 proc namespaces*(self: Key): seq[Namespace] =
   self.namespaces
@@ -271,8 +290,8 @@ proc instance*(
   self: Key,
   id: string): ?!Key =
 
-  without key =? Key.init(id), e:
-    return failure e
+  without key =? Key.init(id), error:
+    return failure error
 
   success self.instance(key)
 
diff --git a/datastore/sqlite_datastore.nim b/datastore/sqlite_datastore.nim
index 0a4d321..d519550 100644
--- a/datastore/sqlite_datastore.nim
+++ b/datastore/sqlite_datastore.nim
@@ -294,9 +294,10 @@ method contains*(
   let
     queryRes = self.containsStmt.query((key.id), onData)
 
-  if queryRes.isErr: return queryRes
-
-  return success exists
+  if queryRes.isErr:
+    return queryRes
+  else:
+    return success exists
 
 method delete*(
   self: SQLiteDatastore,
@@ -328,7 +329,7 @@ method get*(
     queryRes = self.getStmt.query((key.id), onData)
 
   if queryRes.isErr:
-    return failure queryRes.error.msg
+    return failure queryRes.error
   else:
     return success bytes
 
diff --git a/datastore/tiered_datastore.nim b/datastore/tiered_datastore.nim
index 6b2b50a..b19fb56 100644
--- a/datastore/tiered_datastore.nim
+++ b/datastore/tiered_datastore.nim
@@ -3,7 +3,7 @@ import std/sequtils
 import pkg/chronos
 import pkg/questionable
 import pkg/questionable/results
-from pkg/stew/results as stewResults import get, isErr
+from pkg/stew/results as stewResults import isErr
 import pkg/upraises
 
 import ./datastore
@@ -33,11 +33,10 @@ method contains*(
   key: Key): Future[?!bool] {.async, locks: "unknown".} =
 
   for store in self.stores:
-    let
-      containsRes = await store.contains(key)
+    without contain =? await store.contains(key), error:
+      return failure error
 
-    if containsRes.isErr: return containsRes
-    if containsRes.get == true: return success true
+    if contain: return success true
 
   return success false
 
@@ -61,12 +60,15 @@ method get*(
     bytesOpt: ?seq[byte]
 
   for store in self.stores:
-    let
-      getRes = await store.get(key)
+    # the following commented line does not produce the expected result at runtime:
+    # without bytesOpt =? await store.get(key), error:
 
-    if getRes.isErr: return getRes
+    # instead we use intermediate identifier `bopt`
+    without bOpt =? await store.get(key), error:
+      return failure error
 
-    bytesOpt = getRes.get
+    # and now assign `bopt` value to `bytesOpt`
+    bytesOpt = bOpt
 
     # put found data into stores logically in front of the current store
     if bytes =? bytesOpt:
@@ -75,7 +77,7 @@ method get*(
         let
           putRes = await s.put(key, bytes)
 
-        if putRes.isErr: return failure putRes.error.msg
+        if putRes.isErr: return failure putRes.error
 
       break