Apache Pekko

Apache Pekko is a toolkit for building concurrent, distributed, and fault-tolerant applications on the JVM. It was created in 2022 as a community fork of Akka after Lightbend changed Akka's license from Apache 2.0 to the Business Source License. Pekko forked from Akka 2.6.x and released version 1.0 in July 2023, providing a drop-in replacement for projects that need to remain on an open-source license.

The current stable release is Pekko 1.1. The toolkit implements the actor model: lightweight actors process messages sequentially, eliminating the need for locks and shared mutable state in concurrent code. Beyond the core actor system, Pekko includes modules for reactive streams, HTTP servers and clients, cluster formation, and distributed data. It is written in Scala with a Java API, and both the Play Framework 3.x and Apache Flink use Pekko internally.

The official documentation includes migration guides from Akka. The source code is on GitHub under the Apache 2.0 license.