If you have a pub sub cluster that you push revocation details into, and running servers subscribe to that feed and then track a rolling list of tokens that would otherwise still be active but have been revoked, you are effectively storing a revocation database on every edge node.
Again not really. If the pub/sub broker is persistent, you don't have to persist the revocation list on edge nodes. And just pointing out that it's a db in some loose sense of the word doesn't help with the actual challenge of organizing the flow of data reliably in a federated system (i.e. one that can't share a single database).
If you have a pub sub cluster that you push revocation details into, and running servers subscribe to that feed and then track a rolling list of tokens that would otherwise still be active but have been revoked, you are effectively storing a revocation database on every edge node.