How did Knapsack Pro start? In mid-2014 I worked on a client project where we had slow RSpec tests taking ~15 minutes and I was looking for a way to save time and run faster CI builds. I came up with the idea for open source ruby gem called knapsack (idea for the name came from knapsack problem). Knapsack was helping split tests evenly across parallel CI nodes so you could leverage parallelism on CI server.
I added in knapsack readme link to Knapsack Pro beta landing page. Once ~80 people signed up for Knapsack Pro beta then I started building it in March 2015. At the end of 2015, I had a working version and started promoting it. In mid-2016 first paying customers validated it makes sense to improve the product even more. Feedback from users helped me add more features and improvements like Knapsack Pro Queue Mode that splits tests in a dynamic way across parallel CI nodes to ensure each CI node finish work at a similar time. Thanks to that CI build is as fast as possible and there is no bottleneck in your parallel jobs.
Nowadays hundreds of developers use Knapsack Pro every day to run their CI builds faster. The free knapsack gem was downloaded over 60 millions times. Knapsack Pro supports more test runners (not only in Ruby).
Founder of Knapsack Pro