Bitcask is a log-structured hash table for fast key/value data storage. It was developed for use in Riak but can be used as a standalone local key/value store. Bitcask writes new key/value entries by appending to an active file and updates an in-memory keydir. Periodically it merges files to compact data and remove old versions, producing new immutable files. This approach provides low-latency random access, high write throughput, and crash tolerance without losing data.