> Each modification generates a new version of the document. (...) we don’t need it, and there’s no way to disable it (...)

Note that there's a `_revs_limit` setting available: <http://wiki.apache.org/couchdb/HTTP_database_API>. It's very beneficial for a use case like yours.

(Though I've seen CouchDB performing rather poorly when taking really heavy read/write load or compacting big datasets, on occasion.)