The best technical decision I ever made was writing a design doc BEFORE writing code.

It was a RAG system for a financial services client. Complex requirements. Multiple data sources. Strict compliance needs. My instinct was to start coding immediately.

Instead, I spent two days writing a 4-page design document. Problem statement. Proposed architecture. Alternatives considered and why I rejected them. Known risks. Success criteria.

That document caught three major issues before I wrote a single line of code. A data privacy concern I hadn't considered. A scalability bottleneck in my initial architecture. A compliance requirement that would have required a complete redesign at week 6.

Two days of writing saved me at least three weeks of rework.

Now I write design docs for anything that takes more than a week. Not because process is fun — because rework is expensive and frustrating.

The format doesn't matter. A Google Doc, a README, even a detailed comment at the top of your main file. What matters is forcing yourself to think through the problem completely before your fingers touch the keyboard.

Write first. Code second. Debug never (okay, debug less).