Abi built Pull Reminders over the Christmas break of 2017 by using Zapier to receive Slack messages when new pull requests were made on GitHub. From that first MVP he built it as a product (Abi is a developer) and got to over $25k/mo in revenue.
He got his first paying customer in March 2018. So has gone from first paying customer to acquired by GitHub in just over one year!
Here you can read the story of Abi and Pull Reminders (Pull Panda): https://github.blog/2018-10-04-github-developer-story-abi-noda/
He also did an interview with Indie Hackers: From Idea to Profitable Business on the GitHub Marketplace and Slack
You can read the GitHub announcement here: https://github.blog/2019-06-17-github-acquires-pull-panda/