Most of the data stored in Solr has some kind of primary key. Primary keys are different from most of the fields in your data as each document has a unique value stored because they are primary, and in most cases, unique. However, this search on the primary field is not always as fast as you would expect when you compare to other databases. So, is there anything we can do to make it faster? With Solr 4.0, we can, and this recipe will show you how to improve the execution time of queries run against unique fields in Solr.