Leak cheatsheet

Pattern	Symptom	Fix
Accidental global	window.* grows	delete, use let/const, modules
setInterval	CPU + heap over time	clearInterval, store id
Detached DOM	Detached * in snapshot	Clear arrays holding elements
Listeners	Handler count rises	removeEventListener, AbortSignal
Closure	Context retained	Shrink captured scope
Unbounded Map	Entry count = requests	LRU + TTL
EventEmitter	MaxListenersExceededWarning	off / once
Open stream	external grows	destroy(), pipeline()
Module cache	RSS stair-step	Bound or externalize store

Browser debug shortcuts

Action	Where
Heap snapshot	DevTools → Memory
Force GC	Memory → trash icon
Live heap	performance.memory
Perf monitor	More tools → Performance monitor

Node debug shortcuts

Action	Command
Inspector	node --inspect
Expose GC	node --expose-gc
Snapshot	v8.writeHeapSnapshot()
Metrics	process.memoryUsage()

Grafana / K8s (PromQL)

Panel	Query
Working set	container_memory_working_set_bytes{pod=~"app-.*"}
% of limit	working_set / container_spec_memory_limit_bytes * 100
Restarts	increase(kube_pod_container_status_restarts_total[1h])
Leak smell	Memory staircase + flat rate(http_requests_total)

Full walkthrough: Grafana & Kubernetes.

Log grep patterns

FATAL ERROR.*heap out of memory
OOMKilled
MaxListenersExceededWarning