We are in the midst of migrating from some vertically partitioned postgres databases (each with a warm standby) into master/master mysql shards. The PG databas

We are in the midst of migrating from some vertically partitioned postgres databases (each with a warm standby) into master/master mysql shards. The PG databases weren't SPOF's in the worst sense of the word. They could fail over, but this isn't as outage-resistant as the new setup. And we did have more than one, but each was still pretty monolithic. So are most databases for most sites before they've grown up completely. Also, keep in mind that it's pretty easy to code yourself a single point of failure even if your hardware doesn't force it upon you. Working things like that out of a big codebase takes time.