[Spivak]

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.

[skyde]

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.

[Spivak]

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.