So you are on your iPad on a train. Your train goes into tunnel, you lose connection. The application still works because your data is saved in PouchDB. You ex

So you are on your iPad on a train. Your train goes into tunnel, you lose connection. The application still works because your data is saved in PouchDB. You exit the tunnel, you gain connectivity PouchDB syncs your data to the CouchDB on the server. Other devices can now sync from the server.