Is it possible to access documents in a database in CouchDB from another database's design documents?

No, not directly, since only system administrators can access the _users database. However, you could still continously replicate the _users database to a mirror database and treat it like any other database. You can combine several databases with many couchapps into one application via the rewrite list in a design document you use as couchapp. In your Configuration section httpd parameter secure_rewrites should be set to false to allow you to use ../../../ to create a path to another database than the one holding the design document with the rewrite list. Your rewrites in your design document (couchapp) needs to include a rule that point to the database you want to access with a rule e.g. like this: "rewrites": [       {            "from": "users/:email",            "to": "../../../users_mirror/_design/users/_view/by_email"                  "query": {                             "key": ":email",                             "include_docs": "false"                   }        }, ... In this example you would need do have a design document in the _users database (or just in users_mirror) that holds a view that I called by_email. This view could then limit the output from the user database as long as other paths to the database are blocked. You might even want to create a function in a list to add even more security, verifying the role of the user and adding logic. The rewrite would then be something like this {           "from": "users/:email",            "to": "../../../users_mirror/_design/users/_list/userfilter/by_email"                  "query": {                             "key": ":email",                             "include_docs": "true"                   }        } Adding filtering to the replication could add further security to this. Remember: the design document (couchapp) with the view need to be in the same database as the data.

You can use the _rewriter for that by disabling secure_rewrite option in settings and use such rule: {    "from": "/users/*",    "to": "../../../_users/*" }