Comment by brightball
3 hours ago
I think we take for granted how few databases ever outgrow vertical scaling needs.
Usually there will be one or two tables that grow at a dramatically faster rate than everything else and I have always found that those belong in a separate data store.
You need replication for HA. Otherwise the only HA you have is the RAID setup on the one machine. The reason people go horizontal is rarely scale. And if you're doing that you might as well use the passive replica as a read replica.