Ask HN: Any GitHub repos where I can see development over time – simple to big?

You won't find it.

Code grows, decisions get made, and practices are adopted.

I am working on my fourth iteration of what turns out to be my largest undertaking.

Step 1. Idea 2. Hack something 3. Commit, comment. 4. Hit a wall 5. Rewrite, commit, repeat. 6. Grow until new problems are discovered 7. Modules, tests, etc to avoid future problems. 8. New problems caused by complexity. 9. Go to 5.

Read this from Roblox's outage. https://blog.roblox.com/2022/01/roblox-return-to-service-10-...

My recent example - I thought I could get away with 3 VMs to run my SaaS. Yes, I could, although my storage capacity guesses were 100x less than required.

You could inspect the history of any big open source project, no? Pick any popular framework. They may not have created the git project from the very first moment they actually got started but there are so many such projects, if you poke around enough, I'm sure you could find something interesting. As for "best practices", well, you'll probably have to judge that for yourself.