People think Redis is just a cache because the use the puggified version sold by AWS (elasticache). Enable persistence + AOF (the write ahead log) and you got yourself a database.
You can also add your own data structures to Redis, not as a form of syntax sugar over KV pairs, but as a dynamic library that you can write in C/C++/Zig/Rust, where you have full control over the in-memory representation.
But that's also another feature AWS takes away from you if you buy elasticache :^)
I definitely don't consider redis a database since it's not acid compliant and any data you put in you have to be OK with losing. It's still just a cache to me.
I consider it to be cache first, "db" second, with true definition of db first being something that can execute SQL or SQL like statements (such as Cassandra's CQL).
It's the same reason I don't call Cassandra a cache, although it can achieve the same result.
true definition of db first being something that
can execute SQL or SQL like statements
Pedantic note: the term "database" existed long before the relational model or SQL existed. Many of the dominant databases of the 80s and 90s (dBase, etc) would not fit your invented definition.
Additionally, a lot of "toy" databases like Access can execute SQL statements, so the ability to execute SQL statements isn't necessarily a great way to tell what's a "real" database.
In practical terms, I do agree with you -- if somebody in 2023 is referring to "the database" in their app they had darn well better be talking about something robust and ACID-compliant like Postgres or whatever.
