Redis is an in-memory key-value store. Aside from storing simple string-string mappings, it also supports a lot of data structures like sets, lists and queues.
It’s pretty cool.
A lot of Redis alternatives support the Redis protocol (RESP). But there are also ones with different network protocols.
Redis recently switched to a closed-source license. There are many forks, better to move to one of them.
It looks like most of the developer and user velocity is behind Valkey at the moment. You should probably move to that one.
Another fork is Redict.