Solution

Order of Execution

1. Call Stack: Sync code runs first.
2. process.nextTick: Runs immediately after the current operation completes, before the event loop continues. It can starve the I/O loop if abused.
3. Microtasks (Promises): Run after nextTick but before rendering/macrotasks.
4. Macrotasks (Timers/IO):
   • Timers Phase: setTimeout
   • Poll Phase: I/O callbacks (fs, http)
   • Check Phase: setImmediate

Summary

process.nextTick has the highest priority of async operations. setImmediate runs after I/O callbacks in the "Check" phase, making it distinct from setTimeout(0).