To be fair, effectively every majorly popular KV store has different tradeoffs from one another, or different focuses/use-cases. Of course, there are some which are very similar and effectively only differ in implementation, but competition can also be good.
You could say that about programming languages, but they are so useful there end up being a lot of variants.
I searched for a shared memory key value store high and low for interprocess communication and the closest thing I found was WhiteDB. WhiteDB is pretty great, but its concurrency is done through locking and it is very unfortunately GPL licensed, which makes it very niche. (BTW a shared memory key value store for IPC is AMAZING).
There are a ton of key value stores out there though amazingly enough I'm still excited when I see announcements because I haven't found one that is what I want.
That was the first one I tried actually. It was a complete nightmare to get to work on windows and its performance on windows was dismal, as in hundreds of writes per second instead of millions. It was a colossal waste of time.
I suspect that key value store is just the user interface and that whatever heavy lifting there was to be solved is related to tuning for time series data from sensor networks.
