React Re-render Bug Caused 1.4GB Memory Leak and 8-Second Latency Spike

A faulty useEffect dependency loop in a React application triggered a cascading re-render storm, locking container CPU threads at near-100% utilization and allocating roughly 64MB of memory per second until the heap hit 1.4GB. The bug also drove over 4.2 million unthrottled database writes in under 20 minutes before engineers intervened. Sentry's performance monitoring and error tracking tools identified the root cause — un-memoized canvas buffer callbacks in a streaming ECG component — and grouped over 14,000 heap allocation exceptions into a single actionable trace. The fix replaced stateful re-renders with a useRef frame buffer, eliminating the recursive loop entirely. Google AI models, including Gemini 2.5 Flash and MedGemma 27B, were also integrated to cut diagnostic latency from 8.4 seconds down to 1.1 seconds.