Ask HN: Projects to do to get better at distributed systems

For the majority of my career, I've worked as a backend engineer, but now I'm interested in transitioning towards being a distributed systems engineer. I've discovered a great resource at https://pdos.csail.mit.edu/6.824/index.html, which has been very helpful.

I would like to connect with others who have successfully made the transition from backend engineer to distributed systems engineer. What steps did you take, and what side projects did you work on to gain a better understanding of distributed systems?