further, all the relays that use RDBs and NoSQL DBs are automatically indexing all those tags whether you like it or not.
i write database engines from scratch using a KV store, and it's not really that difficult, and the tailoring of the implementation greatly improves performance. i don't think i'm exaggerating when i say that the #orly database engine is the fastest in all of nostr. it uses an engine that is used for a moderately popular graph database called dgraph, and you can't do that shit without highly optimized iteration and log storage strategies.