Find where the same decision is being made twice

A small technical team can keep a surprising amount of product knowledge in conversation. Somebody remembers why an integration retries in a particular way. Another person knows which identity field is authoritative. A third spots a proposal that would conflict with an earlier choice. This works while the people and changes remain close enough for informal correction.

As the team grows, work is split across services, features and delivery streams. New team members start with the code and tickets they can see. Two groups can encounter a similar problem and make reasonable decisions from different parts of the product. The disagreement appears later, when their changes meet.

Look for duplication in decisions before adding more documentation. Pull requests, planning notes, support issues and recurring review comments can show where the team keeps revisiting the same question. Common examples include authentication, error handling, state names, date and timezone treatment, ownership of shared data, API response shapes, audit history and what a user is allowed to reverse.

Write down a decision with consequences rather than a general topic. "We need consistency around dates" does not tell anybody what to do. A decision might say that stored event timestamps use a common reference zone, the user's zone is applied for display, and date-only business rules retain the zone in which the date was chosen. A developer can implement that rule and a reviewer can challenge it.

Trace each repeated decision to the places it affects. If two teams define subscription state separately, identify the database fields, API values, user messages, background jobs and support actions attached to each definition. This reveals whether the differences are deliberate or whether the product now has two meanings for the same word.

Write down both contexts before choosing a version. One area may have a constraint the other does not. The product may need a shared rule, a shared term with explicit variants, or separate concepts with different names.

A short review of duplicated decisions gives the team a practical documentation backlog. It also shows where local autonomy is safe and where an apparently small change can create product-wide disagreement.