blitz.io, the winner of the Best CouchDB app:
CouchDB is the backbone of blitz.io. After some experimentation with various hosted CouchDB’s, we ended up running our own cluster across the virginia and california regions of AWS with multi-master replication between the two regions. We use m1.Large instances and are currently running 1.1.0 though for a while we had both 1.0.2 and 1.1.0 together with a 4-way replication during the upgrade process.
The multi-region deployment is unique because it minimizes the geo latencies to the scale engines described below. Besides this also gives us redundancy, and distributed writes, though at this point in the life of blitz.io we don’t currently shard.
Here is also their Prezi presentation: