Writing a design document or RFC that reviewers can decide on

Goal

Get a substantial change decided by the people who must live with it, on the basis of one document they can read in twenty minutes, before anyone writes the code. The document later serves as the record of why the system looks the way it does.

Prerequisites

A change that is too large or too contested for a pull request description; a known set of reviewers with the authority to accept; a place where the document lives next to the code (a docs/rfcs/ directory, a numbered file, a pull request). PEP 1 (cited) and the Rust RFC template (cited) are public examples of such processes; Google's design-doc templates (cited) require authors to consider security, internationalisation, storage and privacy, with those parts in most cases reviewed by domain experts.

Steps

1. Write the problem statement before any proposal: who is affected, what happens today, which constraint forces a change. If the problem cannot be stated in a paragraph, the document is not ready.
2. List goals as numbered, checkable statements, and non-goals that fence the scope. Non-goals stop the review from expanding into adjacent wishes.
3. Explain the proposal twice, as the Rust template does: a guide-level explanation of how the change looks to a user, then a reference-level explanation with precise semantics, formats and edge cases.
4. Record the alternatives considered and why each was rejected. PEP 1 asks for rejected ideas with the reasoning, so the discussion is not repeated; the Rust template has a rationale-and-alternatives section for the same purpose.
5. State drawbacks, compatibility effects, migration and rollout, and the operational cost honestly; a document without drawbacks reads as advocacy.
6. End with unresolved questions, split into "must be decided in this review" and "can be settled during implementation".
7. Circulate with a review deadline, answer comments in the document rather than in chat, and record the outcome in a status line (draft, accepted, rejected, superseded). Keep rejected documents; they answer the next person who has the same idea.

Expected result

Reviewers argue about the problem and the trade-offs, not about missing context; the accepted document becomes the reference for the implementation and, as the cited Google chapter suggests, a measure at launch of whether the stated goals were met.

Limits and test basis

A design document is not a specification; details change during implementation and the document should say which parts are binding. For small changes the ceremony costs more than it saves. The structure follows the cited templates; no effect on decision quality is measured here.