2025-12-05: Sidekiq queueing SLI apdex SLO violation on catchall-b shard (apdex 61.34%)

Sidekiq queueing SLI apdex SLO violation on catchall-b shard (apdex 61.34%) (Severity 4)

Problem: The 'catchall-b' Sidekiq shard processed jobs slower than the expected SLO, causing a queueing apdex SLO violation.

Impact: Jobs on the 'catchall-b' Sidekiq shard experienced delays, with only 61.34% processed within the target time over the past hour. This affected the timely execution of some background tasks.

Causes: A large backlog built up on the 'catchall-b' Sidekiq shard due to a prior GitLab outage, combined with configuration differences between environments that resulted in monitoring discrepancies.

Response strategy: The backlog was cleared and configuration parity between environments was confirmed. The team reviewed dashboard and queue data to verify job processing has returned to normal.

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This ticket was created to track INC-6127, by incident.io 🔥