Akka implements a unique hybrid of: * Actors , which gives you: * Simple and high-level abstractions for concurrency and parallelism. * Asynchronous, non-blocking and highly performant event-driven programming model. * Very lightweight event-driven processes (create ~6.5 million actors on 4 G RAM). * Supervision hierarchies with let-it-crash semantics. For writing highly fault-tolerant systems that never stop, systems that self-heal. * Software Transactional Memory (STM). (Distributed transactions coming soon). * Transactors: combine actors and STM into transactional actors. Allows you to compose atomic message flows with automatic rollback and retry. * Remoting: highly performant distributed actors with remote supervision and error management. * Cluster membership management. Akka also has a set of add-on modules: * Persistence: A set of pluggable back-end storage modules that works in sync with the STM. * Cassandra distributed and highly scalable database. * MongoDB document database. * Redis data structures database (upcoming) * REST (JAX-RS): Expose actors as REST services. * Comet: Expose actors as Comet services. * Security: Digest and Kerberos based security. * Microkernel: Run Akka as a stand-alone kernel.