That's still a very common pattern if you need maximum performance, and can tolerate small periods of downtime. When designing systems, you have to accept some

That's still a very common pattern if you need maximum performance, and can tolerate small periods of downtime. When designing systems, you have to accept some drawbacks. You can forgo a clustered database if you have a strong on call schedule, and redundancy built in to other parts of your infrastructure. Galera is great, but you lose some functionality with transactions and locking that could be a deal breaker. And up until MySQL 8, there were some fairly significant barriers to automation and clustering that could be a turn off for some people. Everything has it's pros and cons.