From the Dimagi CouchDB success story:
Dimagi became interested in CouchDB after learning about its replication technology. They needed a fully off-line system for each of their clinics, because the only network connection any of them had was an unreliable GPRS modem on the local cellular network. Network outages and latency could not be allowed to disrupt clinic operations.
By standing up a lightweight server at each clinic, backed by a CouchDB datastore, BHOMA was able to ensure constant uptime in the clinics – providing power was up. Each clinic replicates over the modem’s connection to their national CouchDB database. Because of CouchDB’s continuous replication and optimized synchronization, Dimagi didn’t have to worry about writing complicated sync protocols. Filtered replication allowed them to send only the appropriate data to each clinic, drastically reducing the bandwidth required to sync with the central server. The two-way replication also allowed for data collected on CHWs’ cell phones to propagate back to the clinic, for timely patient updates.
Original title and link: CouchDB Case Study: Dimagi - CouchDB Replication at Work (NoSQL databases © myNoSQL)