Hey Engineers/Developers,
I want to practice my backend skills and learn how scalable applications are built. So what I'm thinking to do is learn the high-level system design first and try to implement that learning as well.
Suppose I learned how Instagram reels/TikTok works, how they process, and how they scale to millions of users around the globe by trying to build my own scalable app.
Or I can already contribute to established open-source projects, for example, rocketchat.

What should I do?