I agree the economics here don’t make sense, but leave where? The rest of the world has increasingly strange, or at least unattractive, economics too.
The US is a difficult and long process to get a green card. Other English-speaking countries aren’t necessarily better: Australia seems similar in terms of being a natural resource extraction economy with insanely high real estate prices. Same productivity and salary concerns with the UK.
Apart from network latency, one of the behaviours I've seen with Redis is that reads/write latencies are fairly linearly proportional to the amount of keys queried - which seems to be shown in your chart as well.
We had a different problem, where our monolithic app used both Postgres / Redis for different use cases and worked relatively well. However - it was a lot easier to shove new functionality in the shared Redis cluster. Because Redis is single-threaded, one inconsiderate feature that does bulk reads (100K+ keys) may start to slow down other things. One of the guidelines I proposed was that Redis is really good when we're reading/writing a key, or small fixed-cardinality set of keys at a time, because we have a lot of random things using Redis (things like locks and rate limits on popular endpoints, etc).
However, in your case, I'm guessing Redis shines in the case of a naive single-key (IP address) lookup, but also doesn't do well with more complicated reads (representing your range query representation?). Cool write up overall, I don't have a deeper understanding of how SQLite performs so well when compared to a local Redis instance, so that was unexpected and interesting to observe.
The US is a difficult and long process to get a green card. Other English-speaking countries aren’t necessarily better: Australia seems similar in terms of being a natural resource extraction economy with insanely high real estate prices. Same productivity and salary concerns with the UK.