A simple little process that listens on a changes feed and compiles an index of all the documents it sees by its sequence ID. This allows us to detect any non-deterministic behavior in any of the change events based on the documents it gives us. Its fairly difficult to check this after the fact in couchdb as it fixes itself.
$ npm i -g npm-registry-history
$ npm-registry-history --db path/to/seq.db --seq path/to/registry.seq