Comparing Redis to SQL is kinda off topic. Sure you can replace the one with the other but then we are talking about completely different concepts aren't we?
When all we are talking about is "good enough" the bar is set at a whole different level.
We're talking about business challenges/features which can be solved by using either of the solutions and analyzing pros/cons. It's not like Redis is bad, but sometimes it's an over-engineered solution and too costly
I wrote this article about migrating from Redis to SQLite for a particular scenario and the tradeoffs involved.
To be clear, I think the most important thing is understanding the performance characteristics of each technology enough that you can make good choices for your particular scenario.
https://wafris.org/blog/rearchitecting-for-sqlite