Between 2021-12-12 04:35-04:49 UTC Buildkite's Web, Rest API, GraphQL API, Agent API and Job Dispatch suffered severe degraded performance. API routes that changed the state of builds were particularly impacted. A database migration was applied at 04:35 UTC which resulted in our application throwing errors when attempting to update records. These errors were the result of database columns being deleted, before being ignored in the corresponding application model. We restarted the application which refreshed the application model. This restored our services to normal operation. We subsequently discovered some builds had not been processed. In response, we re-processed in-progress builds around the time of the incident. In the future, we'll be implementing additional internal reviews of database migration changes to prevent recurrence of this situation. We're incredibly sorry for the disruption this outage caused.