Open Source Scala Messaging Platforms

ElasticMQ is a lightweight, fully asynchronous, in-memory message queue implementation written in Scala / Akka. It provides a feature-compatible Amazon SQS REST API interface for testing, local development, or embedded usage. It can persist queues or run purely in-memory and also supports Docker deployment and a web UI.

Kestrel is a simple, distributed message queue system built originally by Twitter. Its design is relatively lightweight and is engineered for speed and simplicity. Kestrel supports queuing patterns such as enqueue, dequeue, and delayed re-enqueue (for example, when a consumer fails to process a message). It stores messages persistently on disk with a memory-backed cache, allowing recovery in case of failures. Because it is intended for relatively simple use cases, it does not provide the full feature set of some enterprise messaging systems, but is often sufficient for many asynchronous or buffered workloads. Over time, the project became inactive and is now archived. Its minimalism and ease of integration made it appealing for smaller or more controlled message-queueing needs.