As a junior dev, I used to take support calls from clients. I realized an overlooked analytics feature was the biggest priority for a majority of our customers, and the UX was lacking at best. I convinced my superiors to allow me to take a crack at it. In a month, I learned Elasticsearch, designed and implemented a complex data vis dashboard. The upgrade was responsible for a 40% reduction in churn. My current challenges are larger in scope, but this taught me a lot very early on in my career.