Node.js EventEmitter memory leak -- MaxListenersExceededWarning

Node.js warns about possible EventEmitter memory leak. The default limit is 10 listeners per event. Happens in long-running servers where listeners are added but never removed.

Do NOT just increase the limit. Find the leak. Common: adding listeners inside request handlers without cleanup. Fix: use .once() for one-time listeners, remove listeners in close handlers, use AbortSignal for cancellable listeners.

Each listener registration adds a function reference. Without removal, they accumulate over the process lifetime.