React Performance: Advanced — Event Handler Refs. Keywords: useeffectevent ref handler. Platform: React/Next.js. Description: Store callbacks in refs for stable effect subscriptions. Do: Use useEffectEvent for stable handlers. Don't: Re-subscribe on every callback change. Good Example: const onEvent = useEffectEvent(handler); useEffect(() => { listen(onEvent) }, []). Bad Example: useEffect(() => { listen(handler) }, [handler]) // re-subscribes. Severity: Low.