[threeseed]

I consult for a lot of companies and I never heard of or seen a database that wasn't horizontally scaled.

It's not for scalability reasons it's for high-availability.

Which as cloud adoption has increased and server uptime has decreased is even more important.

[Spooky23]

Some of these arguments and “common knowledge” things are getting old. Everybody scaled up twenty year ago - hell Amazon used to brag that they used an HP Superdome or whatever.

Anyone with dogmatic opinions about this stuff need to be taken with a grain of salt. If you scale out PeopleSoft, your accounting system will exceed the value of your company. If you’re worried about webscaling your random app, that’s more wasting time navel gazing than accomplishing anything! :)

[jahewson]

Why shard when you can just replicate?

[lmm]

Because replica failover is rarely seamless (and often doesn't actually work at all, IME).

[mikepurvis]

Instinctively that's surprising... replica failover should be far simpler technically, shouldn't it?

[lmm]

No? Replication tends to be a bodged-on mess throughout, full of undertested edge cases, of which failover is definitely one. If you build the system so that nodes joining and leaving is a natural and normal part of operation, well, it naturally works a lot better.