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Documentation-First Development: Building Systems That Last

Documentation-First Development: Building Systems That Last

Most documentation is written after the fact. It's incomplete, inaccurate, and nobody reads it.

Here's a different approach: Write documentation first. Build the system second.

Why Documentation Matters

In a year, you'll forget how this system works. In two years, you'll have completely forgotten. In five years, someone new will need to understand it, and they can't ask you.

Good documentation:

  • Saves time when something breaks
  • Makes onboarding faster
  • Prevents repeating mistakes
  • Makes maintenance easier
  • Helps you think through the design

Documentation-First Development

Instead of "build it, then document it," reverse the order:

  1. Design the system in documentation

    • What problem does it solve?
    • How does it work?
    • What are the key components?
    • What can go wrong?

  2. Get feedback on the documentation

    • Does it make sense?
    • Are there gaps?
    • Is there a better way?

  3. Build it

    • Refer back to your documentation
    • Update as you learn

  4. Verify the documentation is accurate

    • Does it match reality?
    • Is it up to date?

This approach catches design problems before you code.

What to Document

System Architecture

  • Components and how they connect
  • Data flow
  • External dependencies
  • Scaling considerations

Operations

  • How to deploy
  • How to monitor
  • How to respond to failures
  • How to scale up or down

Development

  • How to set up a dev environment
  • Common development tasks
  • Where to find code
  • How to add features

Troubleshooting

  • Common problems and solutions
  • How to debug
  • Where to look for errors
  • Who to contact

Documentation Tools That Work

For architecture: Diagrams (draw.io, Lucidchart) For procedures: Step-by-step with screenshots For code: Inline comments, README files For decisions: ADRs (Architecture Decision Records) For reference: API documentation, database schema

The Discipline

Good documentation requires discipline:

  1. Keep it updated. If it's not accurate, it's worse than useless.

  2. Make it searchable. If people can't find it, they won't use it.

  3. Put it where developers live. In the code repository, not some wiki that nobody visits.

  4. Review it regularly. Every quarter, read it and ask: "Is this accurate?"

Common Documentation Mistakes

  1. Too much. 50 pages of documentation that nobody reads is useless.

  2. Too little. One sentence about a critical system isn't helpful.

  3. Wrong level. Either too technical or not technical enough.

  4. Outdated. Documentation that contradicts reality creates confusion.

  5. Wrong place. If it's not easy to find, it won't be used.

The Goal

Good documentation should:

  • Be accurate. It matches reality.
  • Be current. It's updated when things change.
  • Be complete. It covers what you need to know.
  • Be easy to find. You can search and locate it quickly.
  • Be easy to update. So people actually do it.

Building the Habit

  • Treat documentation like code (version control it)
  • Review it in pull requests
  • Set aside time to keep it current
  • Make it part of your definition of "done"

The Payoff

One day, at 2 AM, something breaks. You look at your documentation. You understand the system immediately. You fix it in 10 minutes instead of 2 hours.

That's documentation-first development.

Create it deliberately. Maintain it religiously. You'll thank yourself.