- Is it true that you only have a single master MySQL server running replication to two slaves, and the architecture doesn’t auto-switch to a hot backup when the master goes down?
- Do you really have a grand total of three physical database machines that are POWERING ALL OF TWITTER?
- Is it true that the only way you can keep Twitter alive is to have somebody sit there and watch it constantly, and then manually switch databases over and re-build when one of the slaves fail?
A 'yes' answer to any of these questions by Twitter would be disturbing to say the least. However, it won't be surprising as companies expect databases to just somehow magically work without creating and supporting a proper architecture. High availability doesn't comes cheap and reputation for companies is everything.
I find it amusing that Twitter isn't even looking for a DBA. May be that's considered a job for the SA over there :)