Memcached vs. ArangoDB vs. Kyoto Tycoon

Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.

A distributed free and open-source database with a flexible data model for documents, graphs, and key-values. Build high performance applications using a convenient SQL-like query language or JavaScript extensions.

Kyoto Tycoon is a lightweight database server with auto expiration mechanism, which is useful to handle cache data and persistent data of various applications. Kyoto Tycoon is also a package of network interface to the DBM called Kyoto Cabinet.