API Lifecycle Management Template

Overview

APIs are long-lived contracts between systems. Changing or removing an endpoint without a structured process breaks downstream consumers, causes outages, and burns trust that takes quarters to rebuild. This template gives you a checklist for the three risky moments in an API’s life: deprecating an old version, shipping a new one, and shutting an API down for good.

The lifecycle only moves in one direction. Every version ends up retired — the open question is whether consumers were ready when it happened:

Related resources: Design a Scalable API Gateway for Microservices, Build Resilient Systems with the Circuit Breaker Pattern, and Dependency Injection.

When to Use

Use this resource when:

• Planning to deprecate an API endpoint or version
• Introducing a breaking change that requires a new API version
• Preparing to shut down an entire API or service
• Auditing whether an in-flight deprecation is actually on track

Skip it when the change is purely additive — a new optional field or endpoint ships on the current version with a changelog entry, not a deprecation plan. For alternatives, see the API Changelog Template.

Solution

# API Lifecycle Management: `<API Name>`

## 1. API Metadata

| Field | Value |
|-------|-------|
| API Name | `name` |
| Current Version | `v2.3` |
| Base URL | `https://api.example.com/v2` |
| Owner Team | `@platform-team` |
| Consumers | Internal: 3, External: 12 |
| Lifecycle State | Published / Deprecated / Sunset / Retired |

## 2. Deprecation Checklist

### 2.1. Decision & Communication

- [ ] Document the reason for deprecation (security, performance, maintainability)
- [ ] Identify all consumers using the deprecated endpoint/version
- [ ] Set a deprecation date (minimum 6 months for external APIs, 3 months for internal)
- [ ] Publish deprecation notice in:
  - [ ] API documentation (changelog)
  - [ ] Developer portal / status page
  - [ ] Direct email to registered consumers
  - [ ] Response headers (`Deprecation`, `Sunset`, `Link` relations)

### 2.2. Migration Path

- [ ] Provide a migration guide with before/after examples
- [ ] Offer a sandbox environment for testing the new version
- [ ] Schedule office hours or Q&A sessions for consumer teams
- [ ] Create a compatibility shim if the migration is complex

### 2.3. Monitoring

- [ ] Track traffic to the deprecated endpoint daily
- [ ] Alert when usage drops below threshold (ready for shutdown)
- [ ] Maintain a dashboard of consumer migration progress
- [ ] Log which consumers still call the deprecated version, not just how many

## 3. Versioning Checklist

### 3.1. Version Selection

- [ ] Determine if the change is backward-compatible (patch/minor) or breaking (major)
- [ ] Follow semantic versioning: `MAJOR.MINOR.PATCH`
- [ ] Update URL path (`/v3/`) or use header-based versioning (`Accept: application/vnd.api.v3+json`)

### 3.2. Release

- [ ] Deploy the new version alongside the old version
- [ ] Update documentation with new request/response examples
- [ ] Run contract tests against the new version
- [ ] Verify backward compatibility for non-breaking changes

### 3.3. Post-Release

- [ ] Monitor error rates and latency for the new version
- [ ] Collect feedback from early adopters
- [ ] Update SDKs and client libraries
- [ ] Record adoption per consumer to seed the next deprecation plan

## 4. Sunset Checklist

### 4.1. Pre-Shutdown

- [ ] Confirm zero traffic to the deprecated endpoint for 7 consecutive days
- [ ] Verify all known consumers have migrated (contact stragglers individually)
- [ ] Announce the final shutdown date (30 days notice)

### 4.2. Shutdown

- [ ] Disable the endpoint (return `410 Gone` or `404 Not Found`)
- [ ] Remove deprecated code and tests
- [ ] Update infrastructure (load balancer rules, DNS)
- [ ] Archive documentation with a redirect to the new version

### 4.3. Post-Shutdown

- [ ] Monitor for unexpected 404s from unknown consumers
- [ ] Document lessons learned
- [ ] Update API lifecycle timeline

Downloadable versions of this checklist, the migration guide, a filled deprecation notice, and the monitoring script below are in the companion repository.

Explanation

The checklist enforces a minimum notice period that respects consumer timelines. External APIs need longer deprecation windows because you can’t control when consumers update — they have release cycles, app store reviews, and frozen change windows of their own. The Sunset header is machine-readable, so client libraries can warn developers automatically instead of relying on humans reading a changelog.

Tracking traffic before shutdown prevents the classic failure mode: an internal cron job or a forgotten mobile app version still hitting the old endpoint on shutdown day. If you can’t name every consumer of a deprecated endpoint, you don’t have a migration problem yet — you have a discovery problem.

URL versioning and header versioning trade off differently. URL versions (/v3/) are explicit, cache-friendly, and easy to grep in access logs. Header-based versions keep URIs stable but are harder to debug and easy for intermediaries to strip. URL versioning remains the most common choice for public REST APIs; pick it unless you have a concrete reason not to.

Versioning Strategy Trade-offs

The versioning decision in section 3 of the template deserves more than a checkbox. Each scheme fails differently:

Scheme	Strengths	Weaknesses	Typical use
URL path (/v3/)	Explicit, cache-friendly, trivially greppable in logs	Pollutes the URL space; old versions linger in bookmarks	Public REST APIs
Custom header (X-API-Version)	Clean URLs	Invisible in browser testing; easy for proxies to drop	Internal APIs behind a gateway
Media type (Accept: application/vnd.api.v3+json)	Versions the representation, not the resource	Awkward to test with curl; weaker caching story	Hypermedia-driven APIs
Query param (?v=3)	Simple to bolt on	Easy to omit; weak default behavior	Rarely recommended for new APIs

Whatever you choose, apply one scheme consistently. Mixed schemes — URL for some endpoints, headers for others — produce consumers that can’t tell which version they’re actually calling.

Deprecation and Sunset Headers

Add HTTP headers to every response from the deprecated endpoint so consumers discover the deprecation programmatically. The Deprecation header (RFC 9745) carries a Unix timestamp marking when the API is deprecated; the Sunset header (RFC 8594) carries the HTTP-date after which the endpoint may stop responding:

HTTP/1.1 200 OK
Content-Type: application/json
Deprecation: @1789430400
Sunset: Sat, 31 Dec 2026 23:59:59 GMT
Link: <https://api.example.com/v3/users>; rel="successor-version",
      <https://api.example.com/docs/deprecation-notice>; rel="deprecation"

Early drafts of the Deprecation header used Deprecation: true; the published RFC uses the @timestamp form. Emit the timestamp and treat any presence of the header as “deprecated” when parsing:

function checkDeprecationHeaders(response) {
  const deprecation = response.headers.get("Deprecation");
  const sunset = response.headers.get("Sunset");
  const link = response.headers.get("Link");

  if (deprecation) {
    const since = deprecation.startsWith("@")
      ? new Date(Number(deprecation.slice(1)) * 1000).toISOString()
      : deprecation;
    console.warn(`Endpoint deprecated since ${since}. Sunset: ${sunset}`);
    if (link) {
      console.warn(`Migration target: ${link.match(/<([^>]+)>/)?.[1]}`);
    }
  }
}

Migration Guide Template

Provide a structured migration guide for each breaking change:

# Migration Guide: v2 -> v3 User Service API

## Summary
- Field `name` split into `firstName` and `lastName`
- Endpoint `/v2/users/{id}` replaced by `/v3/users/{id}`
- Error responses now use RFC 7807 Problem Details format

## Before (v2)
```json
GET /v2/users/123
{
  "id": 123,
  "name": "Alice Johnson",
  "email": "alice@example.com"
}
```

## After (v3)
```json
GET /v3/users/123
{
  "id": 123,
  "firstName": "Alice",
  "lastName": "Johnson",
  "email": "alice@example.com"
}
```

## Error Format Change
```json
// v2 error
{ "error": "User not found", "code": 404 }

// v3 error (RFC 7807)
{
  "type": "https://api.example.com/errors/not-found",
  "title": "User not found",
  "status": 404,
  "detail": "User 123 does not exist"
}
```

## Automated Migration Steps
1. Update base URL from `/v2/` to `/v3/`
2. Replace `name` with `firstName` + `lastName` in request/response models
3. Update error handling to parse RFC 7807 format
4. Test against sandbox at `https://sandbox.api.example.com/v3/`

Automated Sunset Monitoring Script

Track traffic to deprecated endpoints so you know when it is safe to shut them down. This script asks Prometheus — through Grafana’s datasource proxy — for the daily request rate on v2 and counts whole days with zero traffic:

import requests
from datetime import datetime, timedelta, timezone

ZERO_TRAFFIC_DAYS_REQUIRED = 7


def check_sunset_readiness(grafana_url: str, api_token: str) -> bool:
    """Return True when v2 served zero traffic for the required days."""
    headers = {"Authorization": f"Bearer {api_token}"}
    end = datetime.now(timezone.utc)
    start = end - timedelta(days=ZERO_TRAFFIC_DAYS_REQUIRED + 1)

    params = {
        "query": 'sum(rate(http_requests_total{version="v2"}[1h]))',
        "start": start.timestamp(),
        "end": end.timestamp(),
        "step": 86400,  # one data point per day
    }
    resp = requests.get(
        f"{grafana_url}/api/datasources/proxy/1/api/v1/query_range",
        headers=headers,
        params=params,
        timeout=30,
    )
    resp.raise_for_status()
    series = resp.json()["data"]["result"]

    if not series:
        # An empty series means the metric label disappeared — that looks
        # like zero traffic but may be a broken scrape. Verify before acting.
        print("WARNING: no series returned; verify the metric still exists")
        return False

    daily_rates = [float(point[1]) for point in series[0]["values"]]
    zero_days = sum(1 for rate in daily_rates if rate == 0)

    if zero_days >= ZERO_TRAFFIC_DAYS_REQUIRED:
        print(f"READY FOR SHUTDOWN: {zero_days} days of zero traffic")
        return True

    print(f"NOT READY: {zero_days} zero-traffic days in the window")
    print(f"Average daily rate: {sum(daily_rates) / len(daily_rates):.2f} req/s")
    return False

Two details are worth the extra lines. Query with a daily step so one quiet hour inside a busy day doesn’t read as zero traffic — the earlier hourly version counted hours and compared them against days. And treat an empty result as suspicious, not as proof of a dead endpoint: a dropped metric label looks exactly like zero traffic from the outside.

Communicating the Deprecation

A deprecation that consumers never notice is a surprise shutdown. Announce through every channel on the same day, with the same dates, and keep the notice copy-pasteable. A minimal notice looks like this:

# Deprecation Notice: User Service API v2

**Status:** Deprecated as of 2026-09-15. Sunset date: 2026-12-31.

**What changes:** `GET /v2/users/{id}` is replaced by `GET /v3/users/{id}`.
The `name` field splits into `firstName` and `lastName`, and error
responses now use RFC 7807 Problem Details.

**What to do:** Follow the migration guide and test against
`https://sandbox.api.example.com/v3/` before 2026-12-01.

**What happens if you don't:** after 2026-12-31 the endpoint returns
`410 Gone` with a body pointing to the v3 documentation.

**Contact:** platform-team@example.com — office hours Tuesdays 15:00 UTC.

Send it through every channel the checklist names — changelog, developer portal, direct email, and the Deprecation and Sunset headers themselves. Re-send at T-30 and T-7 days with that consumer’s actual traffic stats. “Your integration made 412 calls last week” gets attention that a second generic announcement never does.

Don’t rely on inboxes alone. If the API has a developer portal or dashboard, pin the notice there for the whole deprecation window. If your responses use an envelope or a warnings field, add a deprecated flag with the sunset URL — consumers who only ever see your API through code need the signal in the code path. For long deprecation windows, add a line to the monthly status-page or newsletter cadence so new consumers learn about it before they integrate.

Ownership and Sign-off

Every transition in the lifecycle needs a named approver, or the checklist becomes a document nobody executes:

• Deprecation: the API owner signs off; consumer-facing teams acknowledge the date.
• Sunset date: the owner plus product or support for external APIs; legal reviews partner contracts before the date is published.
• Shutdown: the owner confirms the zero-traffic evidence; an on-call lead confirms the rollback plan if a critical consumer surfaces late.

Write names into section 1 of the template, not just roles. “Platform team” can’t answer a 2 a.m. page.

Variants

Context	Approach	Notes
Internal microservices	Shorter timelines, stricter enforcement	Teams can coordinate via shared Slack channel
Public SaaS API	Long timelines, legal review	May require SLA commitments for deprecation notice
Mobile app backends	Force upgrade via app store	Use minimum app version checks to sunset old endpoints
GraphQL APIs	Schema deprecation directives	Use @deprecated directive on fields and types
Event-driven	Schema registry compatibility modes	Transition from BACKWARD to NONE before removing old schema
Partner/B2B integrations	Contractual notice periods	The MSA overrides internal defaults — read it first

What Works

1. Never remove an API without a deprecation period, even for internal use
2. Return deprecation headers as soon as the decision is made, not at shutdown
3. Maintain a public API changelog with dates for every change
4. Version the API contract independently of the service deployment
5. Keep deprecated endpoints observable with dedicated dashboards
6. Send deprecation notices through multiple channels (email, headers, changelog, status page)
7. Provide a compatibility shim for complex migrations to reduce consumer effort
8. Give every deprecation a named owner who can answer “is it safe to delete this?”

Common Mistakes

1. Announcing deprecation but not tracking whether consumers actually migrate
2. Changing behavior on an existing version without bumping the version number
3. Removing documentation before the API is shut down
4. Assuming all consumers read email announcements
5. Forcing migrations during holiday seasons or fiscal quarter-ends
6. Not providing a sandbox environment for consumers to test the new version
7. Shutting down without monitoring for 404s from unknown consumers post-shutdown

Troubleshooting

• Consumers still call the endpoint after the sunset date: check whether the traffic is shadow traffic, replays, or health checks before assuming real usage. If it is real, extend the sunset rather than breaking consumers silently — but keep the 410 Gone deadline credible by setting a new final date, not an open-ended extension.
• Nobody can say who still uses v2: the consumer registry is stale. Rebuild it from access logs and API keys, then make registration part of onboarding for the next API.
• Version sprawl (v1, v2, and v3 all live): cap the number of supported versions — two majors is a common ceiling — and start the deprecation clock for the oldest the day the new one ships.
• SDKs out of sync with the API: consumers migrated their calls but the SDK still renders the old schema. Version and release SDKs on the same checklist as the API, or generate them from the contract.
• The deprecation email bounced: registered contact lists decay. Review bounces weekly during the deprecation window and fall back to the Link header and the developer portal.

Key Takeaways

• A deprecation is a process with dates, owners, and metrics — not an announcement.
• Machine-readable headers (Deprecation, Sunset, Link) reach consumers who never read email.
• Shut down on evidence — zero traffic for N consecutive days — not on the calendar alone.
• Budget consumer migration time: external consumers move on their release cycle, not yours.

Common Production Pitfalls

These apply to the lifecycle document itself, not to the API:

• Leaving required fields blank or using vague one-word answers.
• Filling the document once and never updating it after scope or decisions change.
• Storing the document where the team does not look during incidents or reviews.
• Not assigning an owner, due date, or review cadence.
• Copying boilerplate without removing sections that do not apply.
• Skipping version control, which makes rollback and accountability impossible.
• Failing to link the document to related decisions or follow-up actions.
• Avoiding quarterly reviews that would retire stale or unused sections.

See Also

• RFC 9745 — The Deprecation HTTP Header Field
• RFC 8594 — The Sunset HTTP Header Field
• RFC 7807 — Problem Details for HTTP APIs
• Semantic Versioning 2.0.0
• Deprecation Timeline Template for planning the calendar side of a sunset.