You deploy a seemingly innocent feature and suddenly CPU spikes from 20% to 95%. Response times triple. The root cause could be a regex gone wrong, a JSON parse on every request, a synchronous loop, or a dependency update. Here''s how to diagnose and fix CPU hotspots in production.
Implement CQRS (Command Query Responsibility Segregation) to scale reads independently from writes. Learn command bus patterns, query bus patterns, eventual consistency, projections, CQRS without event sourcing, testing strategies, and when the complexity is justified.
You scale your app to 3 instances. Your daily billing cron runs on all 3 simultaneously. 3x the emails, 3x the charges, 3x the chaos. Distributed cron requires distributed locking. Here''s how to ensure your scheduled jobs run exactly once across any number of instances.
You store a price as a JavaScript float. You retrieve it as 19.99. You display it as 20.000000000000004. Or you store a BigInt user ID as JSON and it becomes the wrong number. Serialization bugs corrupt data silently — no error, just wrong values.