Documentation And Collaboration

Why this matters for Backend Engineers

Strong documentation and collaboration skills turn good backend engineers into reliable teammates. You’ll ship more predictable releases, reduce rework, and make decisions that future you (and your team) can trust. This skill helps you produce clear specs, log technical decisions, run effective code reviews, plan work with Product and QA, and keep knowledge shareable.

• Fewer misunderstandings: agreements are written, searchable, and reviewable.
• Faster delivery: small, reviewable PRs and clear acceptance criteria.
• Safer changes: risks and rollbacks are thought through before coding.
• Stronger teams: onboarding is smoother and tribal knowledge becomes documentation.

What you’ll be able to do

• Write one-page technical specs that others can implement.
• Record decisions with ADRs so the team can revisit context later.
• Run effective code reviews that improve quality without slowing delivery.
• Plan and estimate work with Product and QA, reducing surprises.
• Share knowledge: run short demos, create onboarding notes, and keep docs fresh.

Who this is for

• Junior to mid-level Backend Engineers who want to ship with less rework.
• Engineers moving toward tech lead responsibilities.
• Experienced ICs who want consistent team practices.

Prerequisites

• Comfort with Git, pull requests, and your team’s codebase basics.
• Basic knowledge of your service’s architecture and dependencies.
• Ability to write clear, concise English.

Learning path (roadmap)

1. Baseline your standards
   Goal: Create a lightweight team doc for specs, ADRs, PR checklist, and coding standards.
   Done when: The team agrees to use it for the next 2–3 changes.
2. Write one small technical spec
   Goal: 1–2 pages covering scope, non-goals, risks, acceptance criteria, and rollout.
   Done when: Product and QA confirm it’s testable; one reviewer approves.
3. Capture one ADR
   Goal: Document a meaningful decision with trade-offs and consequences.
   Done when: Saved where the team keeps ADRs and referenced in the PR.
4. Do review-ready PRs and give great reviews
   Goal: Small PRs with clear descriptions; review at least two other PRs using your checklist.
   Done when: Review time and back-and-forth are noticeably lower.
5. Plan with Product and QA
   Goal: Break a feature into tickets, estimate with assumptions, define acceptance tests and data setup.
   Done when: Estimates, risks, and acceptance criteria are recorded and used.
6. Share knowledge and onboard
   Goal: A 30-minute demo + an onboarding note that helps the next person reproduce your setup.
   Done when: Someone else follows your notes without help.

Worked examples

Title: Add idempotency to POST /payments
Owner: A. Dev | Reviewers: P. Manager, Q. Analyst

Problem
Some clients retry POST /payments on timeouts, creating duplicates.

Goals
- Ensure clients can safely retry within 24h without duplicate charges.

Non-goals
- Changing existing database schema beyond adding a new index.

Design summary
- Clients send Idempotency-Key header.
- Server stores request hash + status keyed by (merchant_id, idempotency_key).
- On retry: return prior result if found.

Risks & mitigations
- Key collisions: include merchant_id in key; validate UUID format.
- Storage growth: TTL records after 24h; index on (merchant_id, key).

Acceptance criteria
- Retried request returns identical response body + status.
- Duplicate charge is not created (verified via db query in QA plan).

Rollout
- Dark launch: log-only mode for 1 day, then enforce.

ADR-007: Adopt Redis for idempotency store
Status: Accepted
Context
We need low-latency read/write for idempotency keys with 24h TTL.

Decision
Use Redis with key: payment:{merchant_id}:{idempotency_key} storing status and response hash.

Consequences
- Pros: Fast operations, TTL built-in, simple ops.
- Cons: Extra infra component; must handle outages with fallbacks.
- Operational: Alert on Redis latency & evictions; document fallback to DB if Redis unavailable.

// Diff (snippet)
func processPayment(req Request) error {
    retryCount := 0 // magic number? why 0 vs 1?
    // ...
}

Bad: "Use a constant."
Good: "Consider a named constant or config setting for retryCount. Today it's always 0, but product may want backoff."

Bad: "This is wrong."
Good: "If processPayment fails after capturing funds, how do we roll back? Could we return a typed error and trigger a compensating action?"

Setup
- Merchant M1, card C1, amount $10.

Tests
1) First request returns 201 Created, payment_id P1.
2) Retry same payload + same Idempotency-Key returns 200 OK with payment_id P1.
3) Different Idempotency-Key creates new payment P2.
4) Missing header returns 400 with message.
5) TTL expiry after 24h allows new payment.

Work items
- Add header parsing + validation: 2h
- Redis integration + TTL config: 1d
- DB fallback path + tests: 0.5d
- Metrics/alerts + dashboards: 0.5d
- QA test data + e2e tests: 0.5d

Assumptions
- Redis cluster already available.
- No schema migrations required.

Risks
- Redis downtime handling (add 20% buffer).

Estimate
~2.5 days + 20% buffer = 3 days.

Drills and exercises

• Spec sprint (15 min): Draft problem, goals, non-goals, and acceptance criteria for your next ticket.
• ADR drill (10 min): Write context, decision, consequences for a recent trade-off.
• PR checklist (5 min): Before opening, confirm small scope, tests, docs updated, clear description, screenshots/logs included if relevant.
• Review practice (15 min): Review a past PR; write 3 constructive comments that suggest outcomes and rationale.
• Estimate t-shirt sizing (10 min): Break a feature into 5–8 tasks with assumptions and a buffer.

Common mistakes and how to avoid them

• Specs that read like essays: Keep to 1–2 pages; move deep dives into details sections.
• Skipping non-goals: Explicitly state what you will not do to prevent scope creep.
• Huge PRs: Aim for 100–300 LOC diffs with focused changes; split refactors from behavior changes.
• Vague acceptance criteria: Make them testable with data, expected codes, and observable effects.
• No decision log: If it’s hard to reverse or affects multiple components, record an ADR.
• Estimates without assumptions: Always write assumptions; add buffer for unknowns.

Mini project: Ship a small feature end-to-end

1. Select a small backend change (e.g., add idempotency to one endpoint).
2. Write a 1-page spec with acceptance criteria and rollout plan.
3. Create an ADR for a key technical decision.
4. Implement in small PRs with clear descriptions and tests.
5. Pair with QA to write and run a mini test plan.
6. Demo the result and write a short onboarding note explaining setup, run, and rollback.

Subskills

• Writing Technical Specs — Plan changes with scope, non-goals, risks, and acceptance criteria.
• ADRs And Decision Logs — Capture context, decision, and consequences for architectural choices.
• Code Review Practices — Make and review PRs that improve quality without blocking.
• Maintainable Code Standards — Write readable, testable code that’s easy to change.
• Working With Product And QA — Align on scope and tests before coding.
• Estimation And Planning — Break work, size tasks, add buffers, surface risks.
• Knowledge Sharing And Onboarding — Keep knowledge documented and reproducible.

Practical projects

• Introduce a PR template and review checklist to your team and measure review time before/after.
• Create an ADR log for your service and migrate 3 past decisions into it.
• Run a 30-minute brown bag on “Writing effective specs,” then pair with a teammate to apply it to an upcoming ticket.

Next steps

• Practice on a real ticket this week using the spec + ADR + PR checklist.
• Take the skill exam below to validate your understanding.
• Keep iterating: after each feature, update docs and note what to standardize for the team.