On the sixth day of Christmas, Chaos Engineering gave to me… 12 systems to test for resiliency! 🎄
Modern tech stacks are vast, interconnected, and sometimes fragile ecosystems. From microservices and databases to CI/CD pipelines and cloud infrastructure, each layer plays a critical role in delivering a smooth, reliable user experience. But when one part fails, it can trigger a domino effect of outages.
That’s why Chaos Engineering isn’t just about testing one component — it’s about stress-testing every part of your stack. In this post, we’ll explore the “12 Systems of Christmas” and how you can apply chaos to each. By running cross-stack experiments, you’ll gain confidence in your system’s ability to weather unexpected failures.
🎁 Bonus Gift: Look out for our fun, holiday-inspired “12 Systems of Christmas” graphic, perfect for sharing with your team!
🎄 1. Microservices: The Ornaments That Hang Together
Where It Fails:
- Service failure: One service crashes and causes downstream failures.
- Cascading failures: Failures propagate due to tight coupling.
- Latency injections: Delays between services lead to slow user responses.
How to Test:
- Use Chaos tools to terminate pods or services randomly.
- Simulate network latency between services to see if SLAs are met.
- Test retry logic and backoff strategies to ensure smooth recovery.
🎉 Pro Tip: Build a “chaos contract” for each microservice. It defines the expected behavior when dependencies fail.
🎄 2. Databases: The Treasure Chest of Christmas Gifts
Where It Fails:
- Failover delays: Primary to replica failovers aren’t instant.
- Replica sync issues: Delays in replication may cause stale reads.
- I/O bottlenecks: High traffic can overload read/write requests.
How to Test:
- Simulate a database failover to ensure systems switch to replicas quickly.
- Test for replication lag to see if downstream systems handle stale reads gracefully.
- Run disk I/O stress tests on databases to ensure slow queries don’t block the system.
🎉 Pro Tip: Use database chaos to prepare for “read after write” anomalies.
🎄 3. Network: The Tinsel that Connects It All
Where It Fails:
- Packet loss: Packets drop between services.
- DNS failures: Services can’t resolve endpoints.
- Network splits: Half of your nodes lose connectivity.
How to Test:
- Run packet loss experiments on services to ensure retries work properly.
- Simulate DNS lookup failures to test if services failover to secondary DNS.
- Create a network partition between nodes or availability zones to see if the system maintains availability.
🎉 Pro Tip: Add “multi-region DNS lookup” as part of your holiday disaster recovery checklist.
🎄 4. CI/CD: The Assembly Line of Holiday Cheer
Where It Fails:
- Broken builds: Build scripts fail or misconfigured dependencies cause errors.
- Failed deploys: Deployment fails mid-process, leaving systems in an in-between state.
- Flaky tests: Tests intermittently pass and fail without clear cause.
How to Test:
- Use Chaos Engineering to interrupt deployments mid-deploy to test rollback mechanisms.
- Deliberately break build scripts to see how quickly your team responds.
- Randomly block network access to CI/CD runners and observe if retries work.
🎉 Pro Tip: Schedule a “Christmas Chaos Game Day” where your team practices responding to CI/CD failures.
🎄 5. Cloud Infrastructure: The North Pole of Your Stack
Where It Fails:
- Region failures: Entire regions go down due to AWS, Azure, or GCP issues.
- Spot instance loss: Spot instances are preempted without warning.
How to Test:
- Use cloud-native chaos tools like Azure Chaos Studio or Gremlin to simulate region outages.
- Deliberately terminate spot instances and see if workloads migrate to on-demand instances.
🎉 Pro Tip: Include “spot instance awareness” in your autoscaling strategy to avoid holiday surprises.
🎄 6. Logging & Observability: The Naughty and Nice List
Where It Fails:
- Logs go missing: Logs disappear, leaving no trace of incidents.
- Alert fatigue: Too many alerts overwhelm on-call engineers.
How to Test:
- Simulate log pipeline disruptions (e.g., disable log agents) to test observability tools.
- Test alert noise suppression by sending bursts of alerts and tracking engineer response.
🎉 Pro Tip: Apply Chaos Engineering to logging to see if alert thresholds trigger before a major incident.
🎄 7. Security: The Silent Intruder of Christmas Night
Where It Fails:
- Certificate expiration: TLS certificates expire, causing service outages.
- API key leaks: Compromised keys expose sensitive data.
How to Test:
- Run experiments to simulate expired TLS certificates.
- Test for API key rotation and ensure no stale keys are in production.
🎉 Pro Tip: Add “check certificate expiration” to your holiday checklist.
🎄 8. Third-Party Services: Santa’s Helpers
Where It Fails:
- External API failures: Third-party APIs fail unexpectedly.
- Rate limits: APIs throttle requests due to sudden spikes.
How to Test:
- Simulate third-party API failures and measure response time.
- Test for rate-limiting to ensure your retries are properly spaced.
🎉 Pro Tip: Use a “mock API” service to simulate third-party failures.
🎄 9. Authentication & Identity: The Password Under the Tree
Where It Fails:
- Identity provider outage: Login services like Okta or AWS Cognito go down.
- Token expiration: Expired tokens cause failed logins.
How to Test:
- Simulate identity provider outages to ensure fallback authentication paths exist.
- Test for expired tokens and ensure users can reauthenticate smoothly.
🎄 10. Storage & Queues: Santa’s Gift Stash
Where It Fails:
- Storage failures: Disk failures, S3 unavailability.
- Queue backlog: Delays in job queues cause processing slowdowns.
How to Test:
- Corrupt S3 objects and see if backup plans activate.
- Simulate queue delays to see if jobs retry properly.
🎄 11. Frontend: The Star on Top of the Tree
Where It Fails:
- Script errors: JS errors leave users with broken pages.
- Content delivery: CDN outages leave assets unavailable.
How to Test:
- Simulate CDN failures to ensure pages render correctly.
- Use chaos testing to break JS functions and see how errors are displayed.
🎄 12. People & Processes: The Heart of It All
How It Fails:
- On-call fatigue: Alerts fatigue on-call engineers.
- Incident miscommunication: Slow incident response.
How to Test:
- Run a “holiday incident drill” to see if teams can respond quickly.
🎉 Which of the 12 Systems do you want to test first? Drop your suggestions in the comments! Let’s build a more resilient holiday stack together.
