Comment by danudey

I worked at a mobile game company for years and years, and our #1 biggest scaling concern was DB write throughput. We used Percona's MySQL fork/patch/whatever, we tuned as best we could, but when it comes down to it, gaming is a write-heavy application rather than the read-heavy applications I'm used to from ecommerce etc.

Sharding things out and replicating worked for us, but only because we were microservices-y and we were able to split our schemas up between different services. Still, there was one service that required the most disk space, the most write throughput, the most everything.

(IIRC it was the 'property' service, which recorded everything anyone owned in our games and was updated every time someone gained, lost, or used any item, building, ally, etc).

We did have two read replicas and the service didn't do reads from the primary so that it could focus on writes, but it was still a heavy load that was only solved by adding hardware, improving disks, adding RAM, and so on.