@ZenCoder
PostgreSQL's synchronous replication would allow you to replicate those critical transactions synchronously, so that they'd be available in two places - the master and a nominated standby - before the transaction was committed. This can of course be very expensive, owing to the fact that the transaction cannot commit until it has remote confirmation, and so is very sensitive to latency. However, the PostgreSQL implementation allows the user to selectively use sync rep per transaction, typically only when it makes business sense to pay the innate performance penalty, for financial transactions and so on. All other transactions are usually committed asynchronously (i.e. there may be a slight delay, typically of a few seconds, before they are visible on standbys).
Full disclosure: I work for the company that developed this feature.
Biting the hand that feeds IT
