While both are document stores, there are some major differences in their data model, most notably that mongoDB uses an update-replaces mechanism, while CouchDB allows you to access any version of a document, which brings with it issues of transaction overlaps (who wins?) and having to periodically compact your database. CouchDB uses a REST interface for all interaction; mongo has programming language-specific drivers (although there are also REST interfaces available), which in many cases can increase performance. Their querying approaches are differnet. Mongo is more akin to a "define an index and use it when possible at query time." CouchDB is more of a "Define a view beforehand and use that view". Oops. I just found a better overview than I can provide, at http://www.mongodb.org/display/DOCS/Comparing+Mongo+DB+and+Couch+DB There are lots of other players in this space, too -- see http://nosql-database.org/ - On Tue, Dec 14, 2010 at 9:12 AM, Thomas Dowling <[log in to unmask]>wrote: > On 12/14/2010 07:58 AM, Luciano Ramalho wrote: > > > > > I believe CouchDB will take the library world by storm, and the sooner > > the better. > > > > A document database is what we need for many of our applications. > > CouchDB, with its 100% RESTful API is a highly productive web-services > > platform with a document oriented data model and built-in peer-to-peer > > replication. In short, it does very well lots of things we need done. > > > Amen. Does anyone have helpful things to say about choosing between > CouchDB and MongoDB? > > > Thomas Dowling > [log in to unmask] > -- Bill Dueber Library Systems Programmer University of Michigan Library