Consider using xxhash vs sha256

[SilentCicero]

You might want to consider a faster hashing algo for ID creation.

Such as:
https://www.npmjs.com/package/xxhashjs

[GAumala]

Maybe there could be an option where user can set his/her own hash function? I'm not sure why is it needed to hash the key before inserting it to the store. Maybe it could also be disabled with this option just by setting the identity function...