2025-12-01: Merged tab on the MR homepage times out

Merged tab on the MR homepage times out (Severity 2)

Problem: The 'Merged' tab on the Merge Request homepage was timing out and returning 503 errors due to backend query timeouts. Impact: All users were unable to access the 'Merged' tab on the Merge Request homepage. Around 3,000 users per hour were affected during the incident. Causes: This MR was identified as the root cause, causing a plan flip leading to query performance issues: gitlab-org/gitlab!212575 (merged) Response strategy: We rolled back the deployment to restore functionality and have since rolled out the revert that permanently resolves the issue.

This ticket was created to track INC-6051, by incident.io 🔥