Hey there! I built a learning-by-doing platform for DevOps, SRE, and all other types of infra engineers - https://labs.iximiuz.com. Started working on the project exactly two years ago, and about 12 months ago added a Premium membership, which immediately took off! Still mind-blown by the results, and it's something I build only in my free (from the main job) time. The labs were making ~$3K MRR for a few months before the Black Friday sale and then doubled the annual revenue in a week by making another ~25K at the end of this November.