Ignore nonce in request caching?

[jessicayuen]

Cache is in the format aggregated_key: {Response, Requests[]}

Request is a pointer to the entire request object, which means that subsequent (N)ACKs (which increments the nonce) are mutating the cache.

This is not breaking because we clean up prior requests, but there is room for optimization here to not constantly mutate the cache on (N)ACKs.