Redis is not a database. it doesn’t have proper transaction support.

it’s basically a cache with a fancy API so you can incrementally update data structure instead of having to constantly write the whole thing you are trying to cache.

Sure it is! Redis is even fully ACID if you use the right persistence settings complete with transactions support and a WAL. You can even set up locking to abort/rollback transactions. In DB parlance Redis’ isolation level is strict serializability which is stronger than Postgres.

If you mean “it doesn’t have every feature of Postgres” and behaves a little differently then sure but it absolutely is a database.

the only way to do an "atomic increment operation" is to use the "Watch" command or to write stored procedure.

Watch is a poor man transaction and stored procedure does not work when you need to read value interactively from somewhere else (user/filesystem/another database) while inside a transaction.

You're literally describing INCR, it's atomic. But I know what you mean, you want atomic GET then SET which is done by WATCH.

I don't disagree with you about WATCH being less powerful than PG transactions. SQLite data types are less powerful than PG types but it's still a database.