Async Didn’t Block — Microtasks Did (Real Node.js Starvation Bug)

This Node.js system didn’t fail because of blocking code.
It failed because of microtask starvation.

A real-time notification service was built using modern async/await, Promises everywhere, and clean architecture. In staging, it worked perfectly. In production, it collapsed.

WebSockets stopped responding

Database queries hung

HTTP requests timed out

CPU and memory looked normal

The event loop wasn’t blocked.
It was starved.

In this video, we break down a real production failure caused by excessive microtasks — where Promise chains monopolized the scheduler and completely starved macrotasks like I/O callbacks.

You’ll learn:

The real difference between microtasks vs macrotasks

Why Promises and async/await can starve I/O

How the event loop drains microtasks before I/O

Why “non-blocking” code can still freeze your system

How recursive Promise patterns collapse at scale

When to use microtasks — and when not to

How senior engineers design for scheduler fairness

This is not theory.
This is how Node.js fails in real systems under load.

If you’re building:

High-throughput Node.js services

Real-time systems (WebSockets, notifications)

Financial or analytics platforms

Event-driven architectures

👉 Understanding microtasks vs macrotasks is mandatory.

🧩 Core Insight

Async is not a performance guarantee.
Scheduling is the real bottleneck.

🏷️ Hashtags

#NodeJS #EventLoop #AsyncAwait #Promises #Microtasks #Macrotasks #BackendEngineering #NodeJSInternals #Scalability #ProductionIssues #SystemDesign