Depends on your uptime guarantees. It becomes a non-issue if you're able to go down for a few moments. Not necessarily viable for some software though, it just

Depends on your uptime guarantees. It becomes a non-issue if you're able to go down for a few moments. Not necessarily viable for some software though, it just depends on what you're running. (Especially because you can apply the migration on slave and subsequently switch master, making this downtime as quick as the time your system needs to do a database switch.) This doesn't apply to big services with millions of users, however.