diff --git a/swarmsim/codex/dhttracker.nim b/swarmsim/codex/dhttracker.nim
index 3a23ddc..04010f7 100644
--- a/swarmsim/codex/dhttracker.nim
+++ b/swarmsim/codex/dhttracker.nim
@@ -16,13 +16,13 @@ type
   PeerDescriptor* = ref object of RootObj
     peerId*: int
     lastSeen*: uint64
-    expiry: AwaitableHandle
+    expiryTimer: AwaitableHandle
 
 type ArrayShuffler = proc (arr: var seq[PeerDescriptor]): void
 
 type
   DHTTracker* = ref object of Protocol
-    expiry*: Duration
+    expiryTimer*: Duration
     maxPeers*: uint
     peers: OrderedTable[int, PeerDescriptor]
     shuffler: ArrayShuffler
@@ -33,7 +33,7 @@ type
   SampleSwarm* = ref object of Message
     numPeers: uint
 
-  PeerExpiry* = ref object of SchedulableEvent
+  ExpiryTimer* = ref object of SchedulableEvent
     peerId*: int
     tracker: DHTTracker
 
@@ -48,11 +48,11 @@ proc new*(
   T: type DHTTracker,
   maxPeers: uint,
   shuffler: ArrayShuffler = RandomShuffler,
-  expiry: Duration = DHTTracker.defaultExpiry,
+  expiryTimer: Duration = DHTTracker.defaultExpiry,
 ): DHTTracker =
   DHTTracker(
     # This should in general be safe as those are always positive.
-    expiry: expiry,
+    expiryTimer: expiryTimer,
     maxPeers: maxPeers,
     shuffler: shuffler,
     peers: initOrderedTable[int, PeerDescriptor](),
@@ -61,6 +61,19 @@ proc new*(
 
 proc peers*(self: DHTTracker): seq[PeerDescriptor] = self.peers.values.toSeq()
 
+proc cancelExpiryTimer(self: DHTTracker, peerId: int) =
+  self.peers[peerId].expiryTimer.schedulable.cancel()
+
+proc createExpiryTimer(self: DHTTracker, peerId: int,
+    engine: EventDrivenEngine): AwaitableHandle =
+  let expiryTimer = ExpiryTimer(
+    peerId: peerId,
+    tracker: self,
+    time: engine.currentTime + uint64(self.expiryTimer.inSeconds())
+  )
+
+  engine.awaitableSchedule(expiryTimer)
+
 proc oldestInsertion(self: DHTTracker): int =
   # We maintain the invariant that the first element to have been inserted
   # must be the oldest. We can therefore return the first element in the
@@ -74,27 +87,20 @@ proc addPeer(self: DHTTracker, message: PeerAnnouncement,
   let peerId = message.peerId
 
   if peerId in self.peers:
-    self.peers[peerId].expiry.schedulable.cancel()
+    self.cancelExpiryTimer(peerId)
 
   elif uint(len(self.peers)) == self.maxPeers:
     let oldest = self.oldestInsertion()
-    self.peers[oldest].expiry.schedulable.cancel()
+    self.cancelExpiryTimer(oldest)
     self.peers.del(oldest)
 
-  let expiry = PeerExpiry(
-    peerId: message.peerId,
-    tracker: self,
-    time: engine.currentTime + uint64(self.expiry.inSeconds())
-  )
-
-  let descriptor = PeerDescriptor(
+  self.peers[peerId] = PeerDescriptor(
     peerId: message.peerId,
     lastSeen: engine.currentTime,
-    expiry: engine.awaitableSchedule(expiry))
+    expiryTimer: self.createExpiryTimer(peerId, engine)
+  )
 
-  self.peers[peerId] = descriptor
-
-method atScheduledTime*(self: PeerExpiry, engine: EventDrivenEngine): void =
+method atScheduledTime*(self: ExpiryTimer, engine: EventDrivenEngine): void =
   self.tracker.peers.del(self.peerId)
 
 proc sampleSwarm(self: DHTTracker, message: SampleSwarm, network: Network) =
diff --git a/swarmsim/codex/types.nim b/swarmsim/codex/types.nim
deleted file mode 100644
index e69de29..0000000