Integration of Solr with AEM/CQ + Zookeeper- better designs

Here we are trying to explain the design approaches when we integrate Solr search with AEM

Solr with CQ: Better designs
When we are in the designing phase of Solr search with CQ, we have different approaches. One of the better approaches is explained below.

How many Solr in a production environment?
For the System to handle abundant requests and fail-safe conditions met, we need to have a minimum of two Solr instances set up and a load balancer on it. So whenever there is a request the load will be balanced and the request will be served.

How the update works?
For updating both Solr through a load balancer, we need to have Apache ZooKeeper configured(http://zookeeper.apache.org/). Zookeeper helps us to serve the configurations across the server.

Can we have XSLT transformation for JSON through this design?
Yes. When we need JSON response from Solr, we have to use our own XSLT files for transformation. This can be kept as usual inside the Solr deployed server (For eg: JBoss).

My changes on XSLT not appearing in the server. How to fix?
After XSLT changes, some times the server cache XSLT files. To get the XSLT files refreshed, we need to follow the below steps.
· Stop JBoss
· Stop ZooKeeper
· Clear temp folders of JBoss
· Start JBoss, ZooKeeper