[yread]

To clarify: let's say I have servers in two locations A and B that are 200ms from each other. When I issue a write to the db in A I don't want to wait (multiples) of the 200ms before it returns. I don't really care whether the write appears to a reader at B in 5s or 50 minutes but of course the writes have to be at least causally consistent.

I won't have millions (realistically not even thousands) of users and the database will be comparatively small.

I've looked at NDB cluster but it feels quite complicated to setup and maintain

[mindcrime]

Consider Couchbase. It uses a combination of asynchronous writes and automatic replication to do a pretty good job of giving low latency writes even at high volume, while also ensuring data integrity. And since reads are served from the cache if possible, you usually get really good read performance as well.

[e12e]

Can you write to a single rdms C, and maybe cache reads at A and B?

[Nican]

Look at MySQL asynchronous replication.