I started Hosted Apache Solr almost 10 years ago, in late 2008, so I could more easily host Apache Solr search indexes for my Drupal websites. I realized I could also host search indexes for other Drupal websites too, if I added some basic account management features and a PayPal subscription plan—so I built a small subscription management service on top of my then-Drupal 6-based Midwestern Mac website and started selling a few Solr subscriptions.
Back then, the latest and greatest Solr version was 1.4, and now-popular automation tools like Chef and Ansible didn't even exist. So when a customer signed up for a new subscription, the pipeline for building and managing the customer's search index went like this:
Original Hosted Apache Solr architecture, circa 2009.