Mergefactor directly carries the impact your search query time and indexing time
Scaling Search Performance
Solr keeps the newly updated index in the most recent segment; if the segment is filled up, it will create a new segment. Solr performs a merge of segments as and when the number of lowest-level segments is equal to mergeFactor, specified in the Solr configuration file. In such a case, it merges all the segments into one. Consider the following case:
curl 'http://localhost:8983/solr/update?optimize=true&maxSegments=2&wa itFlush=false'
While running in the SolrCloud environment, you should be careful while running optimize (forced merge) on your own, instead you can rely on Solr to perform optimization, as a partial merge (that which it does in background).
. Apach JVM from the Azul system is considered to be a high-performance JVM for Solr/Lucene implementations.
Optimizing concurrent clients
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