There's no high performance database that wont take all of your memory (at least for size of data) if you let it.
That's because it's much, MUCH faster to do it that way, though if you can deal with certain type of latency trade offs for throughput something like turbopuffer can do wonders for your costs.
If the data is < ram size and if you read that data again and its off disk again its the slowest it can possibly be, there's a reason most databases implement a buffer cache (actually making writes insanely faster as well) but yeah, MySQL is generally not a very good operational database with all the ones I have tinkered with.
