Comment by rsync

Isn’t this easily solved with sharding ?

That is, one huge table keyed by (for instance) alphabet and when the load gets too big you split it into a-m and n-z tables, each on either their own disk or their own machine.

Then just keep splitting it like that. All of your application logic stays the same … everything stays very flat and simple … you just point different queries to different shards.

I like this because the shards can evolve from their own disk IO to their own machines… and later you can reassemble them if you acquire faster hardware, etc.