Why Builders Should Keep a Decision Log

Published July 15, 2026

Why decisions (not just outcomes) are worth recording

The code shows you what you built. It doesn't show you what you decided against. Six months from now, someone — often you — will wonder why you didn't just use the obvious, simpler approach, and without a record, the only way to answer that is to re-derive the reasoning from scratch, or worse, revisit a path you already ruled out for a reason you've since forgotten. The decisions you rule out are frequently more valuable to remember than the ones you keep, precisely because nothing in the final code hints that they were ever considered.

What a good decision log entry actually contains

A useful entry has three parts: the decision itself, stated in one line; the alternative(s) you considered and didn't choose; and the reason, in a sentence or two, for why you chose what you chose. "Used Postgres instead of Mongo — needed relational joins for the billing/usage relationship, and didn't want to model that in a document store." That's a complete entry. It doesn't need a background section or a pros/cons table — those add friction without adding much recall value later.

How much detail is enough

Enough that future-you, reading it cold with zero other context, understands the decision without needing to ask "wait, why though." That's usually two to four sentences. If it's taking a paragraph or more to explain, that's often a sign the decision was more complicated than it needed to be — or that you're explaining implementation detail that belongs in a code comment, not a decision log.

Making it a habit that survives busy weeks

Log the decision the moment you make it, not at the end of the day when you're trying to remember what happened. The best trigger is: if you paused to weigh two options for more than a minute, that's a decision worth one line in the log, written right then, while the reasoning is still fresh enough to state in a sentence rather than reconstruct later.