ANSWER:

1. The memcached instance that runs behind Couchbase has a hard
   connection limit of 10,000 connections. Couchbase in general
   recommends that you should increase the number of nodes to address
   the distrobution of traffic on that level.
2. The client itself does not have a hardcoded limit in regards to how
   many connections it makes to a Couchbase cluster.
3. Couchbase generally recommends that you create a connection pool
   from your application to the cluster and just re-use those
   connections versus creation and destroying them over and over. On
   heavier load applications, the creation and destruction of these
   connections over and over can get very expensive from a resource
   perspective.
4. Moxi is an integrated piece of Couchbase. However, it is generally
   in place as an adapter layer for clients developers to specifically
   use it or to give legacy access to applications designed to directly
   access a memcached interface. If you are using the Couchbase client
   driver you won’t need to use the Moxi interface.

by Drahkar from http://stackoverflow.com/questions/10351870