I would say there is not much to be gained here, a key value store is just to simple to benefit much from custom logic. You hash the key, you read from or write

I would say there is not much to be gained here, a key value store is just to simple to benefit much from custom logic. You hash the key, you read from or write to a memory location based on the resulting hash. It is pretty likely that with a fast hash function the bottleneck on modern hardware is the memory bandwidth and the same would very likely apply to a FPGA implementation unless you go some extra way to also create some exceptionally fast memory interface. You could likely get some speed-up with dedicated logic to calculate the hashes but what good is that if you afterwards have to wait for the memory?