SwayDB is an open-source, embedded, non-blocking, persistent, and in-memory key-value storage engine designed primarily for Scala but compatible with other JVM languages like Java. It is optimized for fast and efficient handling of large datasets on a single machine but can also be configured to run in distributed environments. SwayDB supports advanced features such as transactions, TTL (time-to-live), and custom serialization, making it highly flexible for a wide range of applications from caching mechanisms to real-time data processing systems.