That advice is a bit dated honestly, Solr is fine but the current "best practice" if you will is to use ElasticSearch.

Not saying you can't do it with Solr or that Solr doesn't scale, it does. You'll just have an easier and more fun time doing it with ES.

Couple of related/examples:

http://highscalability.com/blog/2014/1/6/how-hipchat-stores-...

http://exploringelasticsearch.com/github_interview.html