I have been thinking about this a lot lately. Most React content is about how to do things, but the decisions that really shape a project are the big early ones: architecture, state management, framework choice, rendering strategy.

And with React 19.x, the React Compiler, and Server Components all in the picture, a lot of us are now living with choices we made years ago.

So I’m curious about the experienced people here:

• What was the biggest React/architecture decision you made that you would reverse if you could?
• What did it cost you (time, performance, team confusion, rewrites)?
• What did you learn, and what would you pick today instead?