Binary Install: Systemd config dependencies (Redis & Memcache)?

I’m starting work to figure out how to set up my first Gitea instance. Going with the binary install option on a Debian Linux server I’ve already got running for other services. Debian doesn’t have the prebuilt packages like other distros on the list and don’t want to use snap.

Everything in the instructions seems pretty straight forward. It’s just when I got to the systemd setup instructions I saw that Redis and something I haven’t encountered before called memcached were options listed along with the SQL db options.

My server already has PostgreSQL running for something else and was going to use that. So my question is are these two required? If not what do they enable? The only reference I found for them was outside the installation docs and in the Config Cheat Sheet.

My general understanding is that they seem to be used for the ‘Task’, ‘Indexer’, ‘Que’, ‘Session’, and ‘Cache’ sections. They are an either or choice, so pick one, but are not necessary to use either. Is this correct?

If I did use either what would be the TL;DR of what would be gained?