Performance of the application is one of the most important factors. Of course, there are other factors, such as usability and availability—we could recite many more—but one of the most crucial is performance. Even if our application is perfect in terms of usability, the users won't be able to use it if they will have to wait for minutes for the search results.
The standard Solr deployment is fast enough, but sooner or later a time will come when you will have to optimize your deployment. This chapter and its recipes will try to help you with the optimization of Solr deployment.
If your business depends on Solr, you should keep monitoring it even after optimization. There are numerous solutions available in the market, from the generic and open-sourced ones such as Gangila (http://ganglia.sourceforge.net/) to search-specific ones such as Scalable Performance Monitoring (http://www.sematext.com/spm/index.html) from Sematext.