If you don't want to swap jobs, another way to get very good exposure is to deep dive into any external code base you have access to. I was a sole developer fo

If you don't want to swap jobs, another way to get very good exposure is to deep dive into any external code base you have access to. I was a sole developer for a time, but we had the intention to grow. In preparation I spent a lot of time cleaning up an old codebase to best practices. I pushed every tool and library we used to the limits to get maximum benefit/introduced complexity, which meant reading and understanding the source. My go to language is Scala, and I learned a huge amount from SBT, akka, slick, play and others. Were now up to 4 developers with no official hierarchy, but its agreed that these investments have paid of.