08904ba8__in_Ruby__Python_and_C_Clients__What_should_the_client_do_
[Error Code Received] LCB_KEY_EEXISTS [What does it mean?] The key already exist (with another CAS value) [What should the client do?] 
Keys are unique in Couchbase. Try another key.
Handling Runtime Errors in Ruby, Python and C Clients
What should the client do?