[gaius]

The community has discussed the idea of adding a feature to specify a minimum streaming replication delay

This is a feature of Oracle, the redo logs are replicated to the standbys as normal, so you have an up to date copy of them on the standby, but only applied after an x hour delay. You can roll the standby forward to any intervening point in time and open it read-only to copy data out.

Less need of it these days with Flashback, of course, but it saved a lot of bacon.

[ErikD]

Using mk-slave-delay you can do this with Mysql as well. We always have a slave running behind a day. You can fast forward the slave using the 'START SLAVE UNTIL' command.

[gaius]

Don't MySQL slaves pull from the master, rather than the master pushing? In the Oracle way, the transactions are on the standby, just not applied yet. In the event of a catastropic failure of the primary, you're still covered.