Listen to changes of all databases in CouchDB

I have a scenario where there are multiple (~1000 - 5000) databases being created dynamically in CouchDB, similar to the "one database per user" strategy. Whenever a user creates a document in any DB, I need to hit an existing API and update that document. This need not be synchronous. A short delay is acceptable. I have thought of two ways to solve this:

1. Continuously listen to the changes feed of the _global_changes database.

   • Get the db name which was updated from the feed.
   • Call the /{db}/_changes API with the seq (stored in redis).
   • Fetch the changed document, call my external API and update the document

2. Continuously replicate all databases into a single database.

   • Listen to the /_changes feed of this database.
   • Fetch the changed document, call my external API and update the document in the original database (I can easily keep a track of which document originally belongs to which database)

Questions:

1. Does any of the above make sense? Will it scale to 5000 databases?
2. How do I handle failures? It is critical that the API be hit for all documents.

Thanks!