Explain the Dead Letter Queue (DLQ) pattern. How would you implement failure recovery for asynchronous jobs?

The Event Loop has phases like Timers, Pending Callbacks, Idle/Prepare, Poll, Check, and Close Callbacks.

Each phase has a FIFO queue of callbacks. For instance, the 'Poll' phase retrieves new I/O events, while 'Check' executes setImmediate() callbacks. Understanding this is crucial for debugging race conditions.