By index encoding I just mean putting “encoded” values into the indexed column of your table. Something like this: “city:department:sku”.

This technique is a bit advanced, borrowed from hierarchical databases, and optimizes for specific queries known upfront, so it’s cool but not very flexible. There is a lot more to making it work. You can watch [1], if interested.

But I’d also +1 other suggestions here on fine tuning your db engine and just scaling up the server.

[1] https://youtu.be/jzeKPKpucS0

Disclaimer: I’m with AWS.