Cloudant sits under the Apache CouchDB API, so the easiest path for migration in/out of Cloudant is to use replication to/from another CouchDB-speaking service like Cloudant, Apache CouchDB, TouchDB (mobile), PouchDB (browser). For most databases, you can also get a JSON dump of the document bodies by doing: curl 'https://username.cloudant.com/dbname/_changes | gzip > dbname.json.gz.

The tricker part of course is understanding how to best model data as you move between different database systems. There are some nice tools emerging in the no/new-sql ecosystem to help with that. Here's one that some of our mysql/postgres converted customers seem to like: http://www.foxweave.com/moving-on-premise-data-to-the-cloud-.... My understanding is that it works in both directions.

Chris from Postmark here. We definitely had some trouble over the last few weeks. I am hoping we are beyond that in terms of architecture. So far everything looks great.

Regarding lock-in, this was pretty important to us when we decided to migrate. We prefer to control everything in our data center, so if it came down to it, we wanted that option. Since the Cloudant API is compatible with CouchDB, the migration path is not that hard. Although, considering our impression so far and their expertise, I don't expect it will come to that point.

Thanks for the info Chris. I certainly hope you won't have to make another big move, but vendor lock-in is always a consideration. Also, I'm curious about network/other latency and bandwidth limits when it comes to accessing cloud-based database services. Did you do any measurements on that before or after switching?

...and regards to Natalie, Dana and the rest of the postmark team!

EDIT: noticed info about latency from cloudant on another comment.