Incident Library
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Cases3 cases

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  1. IL-0369 Railway's backend API went down when a column migration waited on locks and replicas could not get database connections
    Railway2025
    Symptoms

    At 15:18 UTC on 9 December 2025, Railway's backend replicas became unhealthy and stopped serving traffic. Dashboard access, CLI operations, logins, the API and the processing of GitHub-based deployments were disrupted, while running deployments stayed online.

    Probe failuresLock contention or deadlockDatabase overloadService outage
    Trigger

    Engineers merged a database schema change with a data migration at 15:03 UTC, and the migration began applying at 15:17 UTC. It added a nullable column to a heavily used table of about 1 billion rows.

    Root cause
    Faulty deployment
    Component
    DatabaseDatabase proxy and connection poolerSchema migrationLiveness and readiness probes
    Contributing factor
    Health check tied to a dependency
    Action items
    • Increase database connections and reconfigure PgBouncer to work within those limits
    • Fix the long-running query so it no longer causes row lock issues
    View case
  2. IL-0554 A database migration used up Sentry US's Postgres connections, and the site and event ingestion were down for 22 minutes
    Sentry2024
    Symptoms

    From 3:42 PM to 4:04 PM PT on 10 October 2024, the Sentry US site and event ingestion were unavailable, and the status page reported an issue with the Postgres database that made the site unavailable. The dashboard, the API and every US ingestion type, including errors, transactions, attachments, profiles, replays, spans, cron monitoring and custom metrics, were affected.

    Service outageDatabase overload
    Trigger

    A database migration ran certain database operations through the RunSQL command without lock and statement timeouts.

    Root cause
    Faulty deployment
    Component
    DatabaseSchema migration
    Contributing factor
    No configuration testsNo runbook
    Remediation
    • Issued a fix, after which the dashboard and ingestion recovered
    Action items
    • Replace RunSQL commands with more robust solutions in the migration framework
    • Update the database framework to the latest version, which handles some operations RunSQL was used for
    • Write runbooks for recovering from lock or timeout issues during migrations
    • Improve alerting and observability so the team reacts sooner
    View case
  3. IL-0391 GoCardless API requests timed out for about 15 seconds while a Postgres migration waited for an AccessExclusive lock
    GoCardless2015
    Symptoms

    Just after a planned Postgres schema migration started, GoCardless received alerts that API requests were timing out. The API was down for about 15 seconds, until the migration went through and the API came back.

    Lock contention or deadlockService outage
    Trigger

    A deploy with a schema migration that renamed the empty invoicing tables and dropped and recreated their foreign key constraints, which referenced some of the most heavily used tables.

    Root cause
    Faulty deployment
    Component
    DatabaseSchema migration
    Contributing factor
    Unverified assumption
    Detection

    Alerts about API requests timing out began just after the schema migration started.

    Lessons

    Avoiding renames of tables in use, table rewrites under an exclusive lock and expensive work while holding one was not enough for GoCardless: a short DDL statement can still cause downtime by waiting in the lock queue behind a long-running query. GoCardless recommends removing long-running queries and transactions from the application and running analytics on an asynchronously updated replica, setting log_min_duration_statement and log_lock_waits to find such queries, setting lock_timeout in migration scripts so a deploy aborts rather than taking the application down, splitting schema changes so locks are held for shorter times, and keeping Postgres up to date. Developers with a console on the production database can cause the same downtime by leaving a transaction open.

    View case
Check your cluster for this

These 3 cases involve Database and Schema migration. kubegap audits a Kubernetes cluster for gaps like these, read-only, from Claude Code or Codex; its checks cite public reports like the ones in this library.

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By root cause1

Faulty deployment3 cases

Component
Database3Schema migration3Database proxy and connection pooler1Liveness and readiness probes1
Contributing factor
Unverified assumption1No configuration tests1No runbook1Health check tied to a dependency1
Organisation
GoCardless1Railway1Sentry1
  1. IL-0369 Railway's backend API went down when a column migration waited on locks and replicas could not get database connections
    Railway2025
  2. IL-0554 A database migration used up Sentry US's Postgres connections, and the site and event ingestion were down for 22 minutes
    Sentry2024
  3. IL-0391 GoCardless API requests timed out for about 15 seconds while a Postgres migration waited for an AccessExclusive lock
    GoCardless2015