Decision Logs: The Missing Artifact in Most Product Teams
Your team is making hundreds of product decisions. Almost none of them are written down. Here is why that is a serious problem — and a lightweight system to fix it.
Six months into a project, someone will ask a question that sounds simple: “Why did we build it this way?”
In most teams, nobody knows. The PM who made the call has moved on, or does not remember, or the decision emerged from three separate conversations that no one documented. Engineering works around the constraint. Product manages the customer. The real answer — “it was a deliberate tradeoff between X and Y, conditional on assumption Z” — is gone.
This is not just an institutional knowledge problem. It is a decision quality problem. The absence of decision records degrades future decisions, slows onboarding, and causes teams to relitigate the same questions repeatedly — each time with incomplete context.
Decision logs fix this. They are simple, low-overhead, and consistently underused.
What Decisions Are Worth Logging
Not everything. The goal is to capture decisions that are:
- Non-obvious: Any reasonable person might have chosen differently
- Consequential: The choice meaningfully affects the product, architecture, or user experience
- Assumption-dependent: The decision is right given a particular belief about users, the market, or technical constraints
Day-to-day tactical choices (copy changes, minor UI tweaks, bug prioritization) generally do not need to be logged. Big-ticket decisions (data model choices, pricing structure, whether to build or buy a capability, how to handle a major edge case) almost always do.
A useful test: if this decision turned out to be wrong in 12 months, would you want to know what you were thinking when you made it? If yes, log it.
The Anatomy of a Useful Decision Log
A decision log entry does not need to be long. Most should fit on half a page. The key fields:
Decision: One sentence stating clearly what was decided. Not the background, not the options — just the decision.
We will build the payroll export as a polling-based system rather than a webhook model.
Date and owner: When was this decided and who is accountable for it.
Context: Two to four sentences on why this decision was being made. What triggered it? What was the live constraint?
The payroll provider integration we are building first (Gusto) does not support outbound webhooks. Our enterprise customers need same-day data consistency. This decision was made under a hard Q3 deadline.
Options considered: What alternatives were on the table? A brief description is enough.
Option A: Webhook model (blocked by Gusto limitation). Option B: Polling every 5 minutes. Option C: Polling on-demand triggered by user action.
Decision rationale: Why did you pick what you picked? Be honest about the tradeoffs.
Polling every 5 minutes (Option B) provides acceptable data freshness for the initial use case and avoids building on-demand trigger infrastructure we don’t need yet. The polling overhead is manageable at current scale.
Assumptions: What beliefs is this decision resting on? This is the most important field.
Assumes: (1) Gusto webhook support remains unavailable for 6+ months; (2) customer demand for sub-5-minute freshness does not emerge in this segment; (3) polling volume stays below X requests/day at current growth rate.
Revisit trigger: Under what conditions should this decision be revisited?
Revisit if: webhook support becomes available, data freshness complaints increase, or polling costs exceed Y/month.
Why Assumptions Are the Most Important Field
Most decisions are not wrong when they are made. They become wrong later — when the assumptions they rested on stop being true.
If you do not write down the assumptions, you cannot tell the difference between “this decision was wrong from the start” and “this decision was right at the time but the world changed.” That distinction matters enormously for how you respond.
It also matters for learning. Teams that log assumptions develop pattern recognition over time. They notice which types of assumptions tend to age well and which decay quickly. They get better at building decisions that are durable.
The revisit trigger is essentially a commitment to review the assumption. Without it, decisions made under one set of conditions persist invisibly long after those conditions have changed.
Where to Keep Decision Logs
The system matters less than the practice. Options that work:
Alongside the code (ADR format): Architecture Decision Records (ADRs) are a well-established format in engineering, typically stored as markdown files in the repository. The benefit is that decisions live next to the code they affect. The limitation is they are engineering-centric and do not naturally capture product decisions.
In a dedicated wiki section: Notion, Confluence, or any other team wiki. The benefit is visibility and searchability. The limitation is that maintenance discipline often degrades over time.
In the PRD or design doc itself: Each PRD includes a decisions section for choices made during the design process. The benefit is that context is preserved inline. The limitation is that decisions are harder to find across documents.
The best system is the one your team will actually use. Start minimal — even a single shared document where anyone can add entries — and evolve from there.
The Onboarding Dividend
Decision logs pay dividends that are hard to see until someone new joins the team.
When a new PM joins and wants to understand why the product is shaped the way it is, they usually get a combination of hallway conversations, tribal knowledge from whoever is willing to talk, and incomplete documentation. Decision logs change this. A new PM who can read six months of decision log entries understands the product’s reasoning, not just its features. They get up to speed faster and make better decisions from day one.
The same is true for engineering. A new engineer who understands why a particular architectural choice was made — and what assumptions it was conditional on — is far less likely to accidentally undermine it without realizing the implications.
A Cultural Point
Decision logs only work if making them is treated as normal and valuable — not as bureaucracy.
The PM who creates a decision log entry should not feel like they are doing extra documentation work. They should feel like they are being thoughtful. The entry should take five to ten minutes to write, not an hour. It should be referenced in retrospectives, cited in future planning discussions, and updated when conditions change.
If decision logs become a compliance exercise — something you fill out because process requires it — they will be useless. If they become a thinking tool that the team genuinely consults, they become one of the highest-leverage artifacts you produce.
Start with your next significant product decision. Write it down. In six months, that entry will be worth more than you expect.