[aq9]

You need to qualify massive scale, it can be on multiple dimensions: * "Large" data (these days, 10s of TB of data, maybe with multi-TB individual tables, billions of rows in the large tables) * "High" QPS - reads * "High" QPS - writes

High QPS is in the eye of the beholder, but let's say something like a few hundred thousand QPS and up.

If you have scale in just one of these 3 dimensions, the solutions are relatively easy (except maybe for high write QPS, depends on the nature of the writes). If you are at scale on all three dimensions, solutions get harder (sharding, non-innodb storage engines).

Of course, there is also the wildcard: the nature of your queries/transactions. Large transactions along with scale will make your life a living hell.