For those who haven't been following along, support for OpenLDAP's MDB (memory-mapped database) library is also available for several other open source projects, including Cyrus SASL (sasldb mech), Heimdal Kerberos (hdb module), SQLite3, OpenDKIM, and MemcacheDB. A work-in-progress patch for Postfix is also available, with a final version coming soon. A backend for SQLite4 is also in the works. A port of Android (JellyBean) for the Motorola Droid4 using MDB/SQLite3 is in progress (since my current phone is a Droid4). Other projects are also in progress and will be announced in the near future. The current list is also posted on http://highlandsun.com/hyc/mdb/ - feel free to suggest other projects.
OpenLDAP MDB completely outclasses other embedded databases (like Oracle BerkeleyDB, Google LevelDB, SQLite, Kyoto Cabinet) from every angle: performance, efficiency, reliability, administrative ease, simplicity, whatever. With MDB not only have we made the world's fastest LDAP server even faster, but we can also make anything else that uses a database even better.
I'll also be presenting an updated talk on MDB at LinuxCon Europe in Barcelona, November 7. http://events.linuxfoundation.org/events/linuxcon-europe/schedule