When I last benchmarked Redis vs. PostgreSQL for a simple k/v cache it was about ~1ms for PostgreSQL to fetch a key, and ~0.5ms for Redis. Faster, but not really noticeably so. I haven't benchmarked SQLite, but I would be surprised if the numbers are substantially different.
Of course Redis can do other things than just a k/v cache, and at scale you just want to offload some load from your main SQL server. But for "small" use cases my conclusion was that Redis doesn't really add anything. OTOH it's also not especially difficult to run so it also not a big problem to use it, but by and large it seems superfluous.
Of course Redis can do other things than just a k/v cache, and at scale you just want to offload some load from your main SQL server. But for "small" use cases my conclusion was that Redis doesn't really add anything. OTOH it's also not especially difficult to run so it also not a big problem to use it, but by and large it seems superfluous.