We currently validate Sprout JoinSplit binding signatures one by one. ed25519-zebra has batch validation math implemented, which tower-batch uses in an integration test to demonstrate its use wrapped in a tower::Service. In fact this was the first test case for the pattern we've used for the async batch RedJubjub signature and Groth16 proof verification. We can use this in our transaction verification pipeline too to get the batch verification speedup.