They are both highly performant key-value stores so it seems like Redis would be a waste. Is my assumption correct?
Probably? Maybe? It depends what you mean by “use redis”. Redis has different performance characteristics than FDB. It has more features, but makes fewer guarantees about reliability. (Unlike FDB, if your redis node goes down, you generally lose access to the data stored there). Are you using redis as a cache? As a message queue? As a KV store? Or something else entirely?
There’s lots of situations redis + fdb might be a great combination. But its impossible to know whether your combination makes sense without knowing more about your architecture.
Oh okay, I had a naive understanding of Redis.