I didn't put a lot of consideration into the algorithm in particular. I was going to do SHA-256 but somebody told me Blake was faster.
I haven't tested the performance of any other algorithms, but that's a completely swappable component. I'm sure the hash function will be swapped with a different one before 1.0.0 is done.
As an example, xxHash [1] would probably get you an easy 5-10x performance improvement over Blake2b. So there are some easy improvements if the cryptographic requirement is not needed.
I haven't tested the performance of any other algorithms, but that's a completely swappable component. I'm sure the hash function will be swapped with a different one before 1.0.0 is done.