I second this AOSA chapter. It's written by the original developers of Berkeley DB, and is at times the only hope of understanding what goes on inside the beas

I second this AOSA chapter. It's written by the original developers of Berkeley DB, and is at times the only hope of understanding what goes on inside the beast that is Berkeley DB. Unfortunately it was written before (or, the original developers have no insight into) several new, and at times, inscrutable features of BDB, such as MVCC (snapshots).