Where can I find the list of all key formats that TiDB uses in TiKV

I’m trying to understand how TiDB stores its data in TiKV. I’ve created a table with a unique index and see a ton of keys in TiKV. Can you tell where I can find some precise information related to how TiDB stores its data in TiKV ? For instance Surreal that can works on top of TiKV has it stored in its code at surrealdb/mod.rs at main · surrealdb/surrealdb · GitHub. Do you have any reference or documentation that could show me the same thing on how TiDB uses TiKV other than by just looking everywhere in the code ?
It seems TiKV prefix some tables with a z but not all of them if I understand correctly which is hard to do at the moment…