How To work with values at reduce functions?

Couchbase Server
2

Try using the Elasticsearch plugin.
Store the json docs in couchbase and XDCR the doc to ElasticSearch. In ElasticSearch you can do ad-hoc and very complex queries better then SQL.
Elasticsearch will bring back a json list of couchbase keys.
In the couchbase SDK do a BulkGet(array_of_keys_in_couchbase) BOOM under a 1 millisecond.

Remember to do not have Elasticsearch store the whole doc or else the rest response from Elasticsearch will kill your speed.

You can get the plugin here http://docs.couchbase.com/couchbase-elastic-search/