Any company with multiple servers in their authentication domain will know of LDAP. Sadly on the Linux platform, OpenLDAP (although arguably the most widely used and well known of the few LDAP servers available) is still not particularly reliable, especially when it comes to replication. The overheads involved in querying even a local OpenLDAP server are much higher than, say, the plaintext files such as /etc/passwd.
Enter nsscache. Created by two boffins at Google (one of whom graduated from Anchor Systems), nsscache gives the reliability and speed of plaintext files (or BDB if you desire) and the scalability of OpenLDAP. Anchor recently started using it and we are confident it will dramatically boost the reliability and lookup speed of all of our LDAP systems.
In terms of performance, we are seeing update times of a second or so for a partial update (only changed or new entries), and around 10 seconds for a full update (replacing the entire on-disk files with a fresh copy of the entire source database) for a bit under 20000 records.
I’d definitely recommend taking a look at it. It currently only operates on Python 2.4 or later (although a patch is nearing release that allows it to work with Python 2.3).