The best replacement for akka is erlang.

The best alternatives to akka are rated as following:
★★★★★  erlang
★★★★  storm
★★★★  vert.x
★★★  finagle
★★★  netty
★★★  jms
★★  kafka
★★  scala actors

Your alternative for akka is not listed? Suggest!
Speaking about akka, one probably shouldn't forget about kafka.

Other search terms related to akka and their ratings are:
★★★★★ kafka
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akka
erlang
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