| name | tech-design-doc |
| description | Use when authoring, scaffolding, or auditing a technical design doc, RFC, ADR, technical spec, or architecture proposal — for any audience including external dev partners. Triggers include "design doc for X", "I need an RFC", "should this be an ADR or a full design doc", "help me prep for the architecture review meeting", "audit this design doc". Skip for product plans / PRDs, single-line decisions that fit in a commit message, post-mortems, or process-only meeting agendas without architectural content. |
Technical Design Doc
The only thing a design doc optimizes for is decision quality — can a reasonable reviewer make the right call from this doc in one meeting. Most "bad" design docs aren't bad at writing; they're bad at triage. Get the format right and 70% of the work is done.
Triage first (do this every time)
Q1. Recording a decision already made, OR seeking buy-in?
└─ recording → ADR (~1 page)
Q2. Buy-in: how many stakeholders?
├─ 1-3 your team → standard RFC (4-6 pages, 60-min review)
├─ 4-10 cross-team → standard RFC + formal approvers list
└─ org-spanning / infra → heavyweight (10-20 pages, KEP + PRR)
Q3. Audience is an external partner (different company)?
└─ yes → switch to partner-mode (adds glossary, ownership table, "proposing" tone)
Default if unsure: standard RFC. Need evidence to grow heavyweight or shrink to ADR.
Edge cases (PR/FAQ vs design doc, splitting, when ADR should grow into RFC) → reference/triage.md.
Templates
| Template | Pages | Meeting | When |
|---|
mini-adr.md.tmpl | 1-2 | 30 min or async | Decision already made — recording it. Nygard format. |
standard-rfc.md.tmpl | 4-6 | 60 min | Buy-in for a non-trivial design, one team. Rust-RFC skeleton. |
heavyweight-doc.md.tmpl | 10-20 | multi-week | Org-spanning, infra-sensitive. KEP + Production Readiness Review. |
partner-doc.md.tmpl | flexible | varies | External dev partner. Standard + glossary + ownership table. |
Workflow
1. Triage → pick template
2. Scaffold → scripts/new-doc.sh --template <t> --slug <s> --title "..."
3. Outline (BLUF) → Summary + Goals/Non-Goals first
4. Alternatives → ≥3 alternatives BEFORE detailing the proposal
5. Design → proposal + diagrams (C4 context + sequence)
6. Cross-cutting → fill checklist; mark N/A explicitly with reason
7. Audit → scripts/audit-doc.py <file>
8. Pre-read → distribute 24h before meeting (48h for partner-mode)
9. Decide → meeting (or async) → status flips
10. Log → scripts/append-decision-log.py → row in DECISIONS.md
11. (optional) Sync → gdoc-sync to a live Doc
House rules (audit enforces 6 of 10)
- BLUF. First paragraph names the decision being requested, not the background.
- Quantify goals — replace adjectives with numbers. ("scalable" → "10× peak, p95 ≤ 300ms"). See reference/non-goals.md.
- Alternatives, scored on consistent axes. Standard RFC and heavyweight: ≥3 alternatives (status quo + incremental + proposal at minimum). Mini-ADR: 2-3 inline brief alternatives are fine — narrower decision, lighter requirement. See reference/alternatives-considered.md.
- Non-goals are load-bearing — they prevent 80% of scope-creep arguments.
- No happy-path-only diagrams. Show retries, timeouts, failure paths. See reference/diagrams.md.
- Cross-cutting checklist every time — security, privacy, observability, rollout, scalability, dependencies, failure modes, on-call. Silent omission forbidden; N/A with reason is fine. See reference/cross-cutting-checklist.md.
- Status header mandatory — Version, Author, Status (Draft/In-Review/Accepted/Rejected/Superseded), Approvers, Decision date.
- Be opinionated — your job is to propose. If genuinely no opinion, say so explicitly and commit to that posture.
- Length matches scope — 2 pages → 30-min, 6 pages → 60-min, >6 pages → split or escalate. Past these breakpoints, comment volume goes nonlinear.
- End with Next Steps, not approval — phases, owners, dates, metrics. Approval is the start.
The why behind each rule + 9 documented anti-patterns: reference/anti-patterns.md.
Reference docs (load on demand)
Scripts
| Script | What |
|---|
scripts/new-doc.sh --template <t> --slug <s> --title "..." | Scaffold from template into ./drafts/design-<slug>-v1.md |
scripts/audit-doc.py <file> | Static checks against house rules; non-zero on errors |
scripts/append-decision-log.py <file> | Append one row to DECISIONS.md after Accepted |
Output: ./drafts/design-<slug>-v1.md + ./drafts/DECISIONS.md. Never overwrite a previous version without asking.
When NOT to use
- PRD / product plan — vision-first, customer-first. Different shape.
- Brainstorm / sketch — too early. Free-form notes; escalate when ready for buy-in.
- Single-line decision — write a commit message; don't ADR-ify trivial things.
- Post-mortem / incident review — separate format (timeline → root cause → corrective actions).
Cross-skill calls
gdoc-sync — push the finished doc to a live Google Doc for stakeholder comments.presentation-generator (optional) — derive an exec-summary deck from the doc's Summary + Goals + Alternatives.prompt-engineer (optional) — for LLM/agent design docs, reference its prompt-engineering guidance.
