WS1: API-Served Systems (Deprecation, Sunset, Cut-Off) For API-served systems, the provider implements a three-phase deprecation sequence. Phase 1 (deprecation notice): the API documentation is updated with the shutdown date, and a sunset header is added to API responses indicating the withdrawal timeline. Phase 2 (sunset period): the API continues operating at full functionality through the deprecation period, giving deployers time to migrate. Phase 3 (cut-off): on the announced date, the API begins returning HTTP 410 Gone responses with a body explaining the system’s withdrawal. Post-cutoff access attempts are logged for the decommissioning record. API gateway configurations (AWS API Gateway, Kong, Apigee) can automate the deprecation sequence: adding sunset headers, switching to 410 responses after the cutoff, and logging post-cutoff attempts. The automation reduces human error and provides a verifiable record. Key outputs

• Three-phase API deprecation (notice, sunset, cut-off)
• Sunset header on API responses during deprecation period
• HTTP 410 Gone with explanation after cut-off
• Automated via API gateway configuration