Switching to a cached version of Stack.empty, saving 16 bytes per Actor. Switching to purging the Promises in the ActorRefProvider after successful creation to conserve memory. Stopping to clone the props everytime to set the application default dispatcher, and doing a conditional in ActorCell instead.

akka-actor/src/main/scala/akka/routing/ConnectionManager.scala

@@ -40,6 +40,12 @@ trait ConnectionManager {
    */
   def size: Int
 
+  /**
+   * Returns if the number of 'available' is 0 or not. Value could be stale as soon as received, and this method can't be combined (easily)
+   * with an atomic read of and isEmpty and version.
+   */
+  def isEmpty: Boolean
+
   /**
    * Shuts the connection manager down, which stops all managed actors
    */
@@ -90,6 +96,8 @@ class LocalConnectionManager(initialConnections: Iterable[ActorRef]) extends Con
 
   def size: Int = state.get.connections.size
 
+  def isEmpty: Boolean = state.get.connections.isEmpty
+
   def connections = state.get
 
   def shutdown() {