Data Validation before entry into Couchbase server?
You can validate the input by adding another entity "validate_doc_update" to the _design/ document.The validate_doc_update function gets executed for each document you want to create or update. If the validation function raises an exception, the update is denied; when it doesn’t, the updates are accepted. 
It is optional i.e. if you do not write one, no checking will be done.

More details can be found on http://guide.couchdb.org/draft/validation.html