Incident with Pull Requests

Summary

Incident with Pull Requests

On May 6, 2026 between 15:12 and 19:02 UTC creation of new pull request review threads on GitHub.com failed. This included new line comments and file comments on pull requests. Existing PRs and previously created comments were unaffected. <br /><br />This incident was caused by a 32-bit integer key reaching its maximum value in a Vitess lookup table used during PR thread creation. The primary table had been migrated to a 64-bit integer key but the Vitesse lookup table remained 32-bit. Once the values in the primary table passed the available 32-bit ID space in the lookup table, attempts to create new review threads began failing, resulting in near 100% failure rate for new thread creation requests. We mitigated the issue by updating the impacted lookup table definitions across all shards to use 64-bit integer column types, increasing the available ID range and restoring normal operation. Service was fully restored once the schema changes competed globally. <br /><br />To help prevent similar incidents, we are expanding existing monitoring of database columns to include Vitess lookup tables to notify in advance of any tables that is approaching a column size limit. This work is intended to provide earlier detection of columns approaching size limits before customer impact occurs.

• Started

  May 6, 2026 · 3:25 PM

• Resolved

  May 6, 2026 · 7:04 PM

• Duration

  3h 39m

• Severity

  Critical

• ◐

  Investigating

  May 6 · 3:25 PM GitHub

  We are investigating reports of degraded performance for Pull Requests

• ◐

  Investigating

  May 6 · 3:28 PM GitHub

  We are investigating failures for new thread creation on Pull Requests. Responses to existing pull request threads are unaffected.

• ◐

  Investigating

  May 6 · 3:55 PM GitHub

  Creation of new Pull Request threads (including line and file comments) continues to be affected. We have identified the cause of the issue and have started taking steps to mitigate this issue.

• ◐

  Investigating

  May 6 · 4:07 PM GitHub

  Pull Requests is experiencing degraded availability. We are continuing to investigate.

• ◐

  Investigating

  May 6 · 4:20 PM GitHub

  Creation of new Pull Request threads (including line and file comments) continues to be affected. <br /><br />Top-level comments on pull requests still function and should remain usable during recovery. Opening and merging pull requests, actions, and other pull request operations remain functional. <br /><br />A mitigation is being applied. Recovery is expected to be gradual, with complete recovery expected by 8:00pm UTC.

• ◐

  Investigating

  May 6 · 5:52 PM GitHub

  Creation of new Pull Request threads (including line and file comments) continues to be affected although we are seeing partial recovery.<br /><br />A mitigation is being applied to continue to accelerate recovery with complete recovery expected by 8:00pm UTC.<br /><br />Top-level comments on pull requests still function and should remain usable during recovery. Opening and merging pull requests, actions, and other pull request operations remain functional.

• ◐

  Investigating

  May 6 · 7:04 PM GitHub

  Mitigations have been fully applied and we are seeing full recovery of functionality on Pull Request threads. We are continuing to monitor to ensure sustained recovery.

• ✓

  Resolved

  May 6 · 7:04 PM GitHub

  On May 6, 2026 between 15:12 and 19:02 UTC creation of new pull request review threads on GitHub.com failed. This included new line comments and file comments on pull requests. Existing PRs and previously created comments were unaffected. <br /><br />This incident was caused by a 32-bit integer key reaching its maximum value in a Vitess lookup table used during PR thread creation. The primary table had been migrated to a 64-bit integer key but the Vitesse lookup table remained 32-bit. Once the values in the primary table passed the available 32-bit ID space in the lookup table, attempts to create new review threads began failing, resulting in near 100% failure rate for new thread creation requests. We mitigated the issue by updating the impacted lookup table definitions across all shards to use 64-bit integer column types, increasing the available ID range and restoring normal operation. Service was fully restored once the schema changes competed globally. <br /><br />To help prevent similar incidents, we are expanding existing monitoring of database columns to include Vitess lookup tables to notify in advance of any tables that is approaching a column size limit. This work is intended to provide earlier detection of columns approaching size limits before customer impact occurs.