Documentation Strategy for Startups: What to Write and What to Skip

Documentation at startups sits at one of two extremes. Either nobody writes anything and all knowledge lives in people is heads, or someone creates a Notion workspace with 200 empty pages and a taxonomy that nobody follows. Both approaches fail. The first creates catastrophic knowledge loss when people leave. The second creates an illusion of documentation that nobody reads or maintains.

What to document at each stage

Pre-product-market fit (1 to 10 people): Write almost nothing. At this stage, your product is changing every week. Documentation will be outdated before the ink is dry. The only things worth documenting are: how to set up the development environment, how to deploy, and how to access production systems. These three documents save hours every time someone joins or when you need to deploy at 3 AM and the one person who knows how is on vacation.

Post-product-market fit (10 to 30 people): Now you need more. Add architecture decision records (ADRs) for significant technical choices. Add runbooks for common operational tasks. Add onboarding documentation for new engineers. Add API documentation if you have external integrations. These documents reduce the time it takes for new hires to become productive and prevent knowledge from being siloed in individual engineers.

Growth stage (30+ people): At this point, you need a documentation culture. Every new system should come with documentation. Every incident should produce a postmortem. Every process change should be reflected in the relevant runbook. Assign ownership of documentation areas to specific teams.

Architecture Decision Records

ADRs are the single most valuable type of documentation for an engineering team. An ADR captures why you made a technical decision, not just what you decided. Six months from now, when someone asks "why are we using RabbitMQ instead of SQS?" the ADR explains the context, the options you evaluated, and the tradeoffs you considered.

Keep ADRs short. Title, date, status, context, decision, and consequences. Each one should fit on a single page. Store them in your code repository, not in Notion or Confluence. Documentation that lives next to the code is more likely to be found and maintained than documentation in a separate tool.

Runbooks over wikis

A wiki page titled "Database Operations" with ten paragraphs of prose is useless at 3 AM when the database is down. A runbook titled "Database: Connection Pool Exhaustion" with numbered steps, specific commands, and expected outputs is useful. Write runbooks, not wikis.

Every runbook should follow the same format: symptoms (how you know this problem is happening), diagnosis (commands to run to confirm), resolution (step-by-step fix), and escalation (who to call if the fix does not work). Test your runbooks by having someone who did not write them follow the steps. If they get stuck, the runbook needs revision.

What to skip

Do not document things that change frequently. Feature specifications that are updated weekly are better served by a living product document that is owned by a specific person, not a wiki page that becomes stale. Do not document code that is self-explanatory. Good function names and clear variable names are better documentation than comments that say "increment counter by one."

Do not build a documentation taxonomy before you have documentation. Start by writing the documents you actually need. Organize them later when you have enough content to see natural categories emerge.

Making it stick

The only way documentation gets written and maintained is if it is part of your workflow, not a separate activity. Include documentation updates in your definition of done for new features. Add runbook creation to your incident response process. Review documentation during onboarding and fix anything that is wrong or missing.