Sqlite is always a good option if you want in-memory and SQL. Kyotocabinet supports a number of in-memory database types, as does its networked counterpart kyot

Sqlite is always a good option if you want in-memory and SQL. Kyotocabinet supports a number of in-memory database types, as does its networked counterpart kyototycoon. BerkeleyDB can be effectively run in memory if you size your cache right, and as a bonus you can build bdb with a sqlite frontend. Anyway, cool post. For more lua, there's openresty (nginx and lua), and kyototycoon supports lua scripts as well.