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Intermediate Topic 19 of 51 Concurrency & Parallelism

Event-Driven Concurrency

Single-threaded handling of many tasks via an event loop.

How it works

A single thread runs an event loop dispatching callbacks as I/O completes using epoll/kqueue, handling thousands of connections with little memory (Node.js, nginx).

Where it is used

I/O-heavy servers.

Common pitfall

CPU-heavy callbacks block all other events.

Where it fits in the course

Event-Driven Concurrency is topic 19 of 51 in Concurrency & Parallelism, rated Intermediate. It follows Async/Await. The next topic is Coroutines.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Concurrency & Parallelism quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is Event-Driven Concurrency?
Single-threaded handling of many tasks via an event loop. It belongs to Concurrency & Parallelism and is an intermediate-level topic.
Where do people use Event-Driven Concurrency?
I/O-heavy servers.
What is the most common mistake with Event-Driven Concurrency?
CPU-heavy callbacks block all other events.
What should I learn before this topic?
Start with Async/Await, the topic just before it in Concurrency & Parallelism.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Concurrency & Parallelism quiz.
Is Event-Driven Concurrency hard to learn?
It is an Intermediate topic. Be comfortable with the Beginner topics in this area first, then read the common pitfall carefully, since it is where most mistakes happen.
How long does it take to learn Event-Driven Concurrency?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Event-Driven Concurrency?
Async/Await, Coroutines, Priority Inversion are closely connected. The full list is in the related topics section of this page.
What should I study after Event-Driven Concurrency?
Continue with Coroutines, the next topic in Concurrency & Parallelism.

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