Typical Postmortem Report : Web Application Service Downtime

Issue Summary:

Outage Duration: August 15, 2023, 10:45 AM - August 15, 2023, 12:30 PM (UTC)

Impact: Web Application Service Downtime

Users Affected: Approximately 25% of users experienced service disruption, leading to slow loading times and intermittent errors during the outage.


  • 10:45 AM: The issue was detected through automated monitoring alerts indicating a sudden spike in error rates and increased response times.

  • 10:50 AM: On-call engineer initiated investigation after receiving the alert, suspecting a possible database overload due to recent feature updates.

  • 11:05 AM: Initial investigation focused on the database cluster, as its performance metrics showed signs of high utilization. Assumption: Increased load from new features may have caused the degradation.

  • 11:30 AM: Additional debugging revealed no significant issues with the database; attention shifted to application server logs, suspecting a potential code regression.

  • 12:00 PM: A separate team escalated the incident to higher management as the service degradation continued, impacting a substantial user base.

  • 12:15 PM: A collaborative effort began between the development and operations teams to explore multiple avenues, including network latency and third-party integrations.

  • 12:30 PM: The root cause was identified and resolved: a misconfigured caching layer was inadvertently triggered by recent updates, causing data inconsistencies.

Root Cause and Resolution:

Root Cause: The recent feature updates introduced a misconfiguration in the caching layer, leading to incorrect data being served, resulting in increased database load and performance degradation.

Resolution: The misconfiguration was traced back to an update in the caching logic that lacked proper validation of cached data. The issue was promptly addressed by rolling back the caching logic to a stable version and deploying a hotfix to all affected servers.

Corrective and Preventative Measures:


  • Implement stricter code review processes for caching-related changes to prevent similar misconfigurations in the future.

  • Enhance monitoring and alerting systems to provide early warnings for abnormal cache behavior.

Tasks to Address the Issue:

  1. Roll out the hotfix to all servers and verify its effectiveness through thorough testing.

  2. Conduct a comprehensive review of recent feature updates to identify any other potential configuration issues.

  3. Update the incident response plan to ensure clear communication channels and well-defined escalation paths.

  4. Organize a post-incident meeting to discuss the lessons learned and implement best practices for avoiding similar incidents.

By adhering to these corrective measures and addressing the tasks outlined, we aim to prevent future incidents stemming from misconfigurations and enhance our ability to detect and mitigate issues in a more timely manner. We understand the impact this outage had on our users and are committed to providing a more robust and reliable service moving forward.