Latency POSTing to the /inbox
After some exploratory work in !3985 (closed) it's clear that there's less than ideal performance with POSTing to an inbox under some conditions. The primary issue is related to signature validation when we have to fetch the actor's public key. If either server is under load it can really increase the time to process the request to several seconds or more.
I think it may be possible to do some kind of "optimistic" validation where if we have the key and can validate immediately we should do so, otherwise we should accept the activity and delay the signature validation until the Oban job executes to process the activity.
Does this seem like a reasonable approach?