ES Configuration across geographies

We have just started using ES (1.5.2) and so not so expert in config settings, so need some help here.

We have 1 cluster with 4 nodes, 2 sitting in UK and 2 in NY and rest all settings, shards,replicas etc are default. We are experiencing issues in performance with search. data is less around 0.4 millions records only. i doubt that may be some requests from UK are going to NY too because of data distribution across nodes and this causes delay. We want that UK request are answered in UK only and NY in NY only . As for same data in our test env we have 1 cluster/1 node and all comes under 1 sec. can someone please suggest what should be our config settings to achieve max performance .

Then you are better off having two discreet clusters with the same data.
Otherwise ES will send requests to both!

thanks Warkolm, does ES offer support to keep 2 clusters in Synch automatically for updates ?

Not currently.

thanks. Any other option we have other then having multiple clusters and still able to gain in performance . Please suggest