EventLoop vs. ThreadPool: Which One Should You Use and When?

Ever wondered how apps handle multiple tasks at once? That’s where ThreadPools and EventLoops come in. One uses multiple threads to juggle tasks, while the other relies on an async, non-blocking approach. But which one should you use?

In this post, we’ll break down ThreadPools vs. EventLoops, how they work, and when to pick one over the other—without the boring theory. Let’s dive in!

ThreadPool

Simply put, it is a collection of worker threads that are already present, and when a task comes, it is assigned to an available thread. Once the task finishes, the thread is released and made available for other tasks.

Pros

• Good for parallelizable tasks
• Reduces overhead for creating and destroying new thread for each task

Cons

• Less efficient for I/O bound as once the pool gets exhausted, the incoming processes need to wait until a thread is available
• Can lead to deadlocks and race conditions if proper synchronization methods are not implemented

EventLoop

It is a single-thread mechanism that executes asynchronous processes one at a time. To explain asynchronous processes, they are the processes that execute later in time rather than immediately.

For example, when you open a stock market app, it fetches data from multiple sources. Since all the data can’t load instantly, the app displays it as it arrives. That’s why stock prices appear one by one—this is an asynchronous process.

Pros

• Less overhead since it runs on a single thread
• Good for I/O-bound operations such as network requests, database queries, file I/O, etc

Cons

• Not efficient for CPU-intensive tasks since it will consume a lot of time for execution
• Helps achieve concurrency

So if you want to execute multiple tasks at once, ThreadPool is to-go.

And want to achieve data consistency? EventLoop is there for you!

That's it, folks! Let me know in the comment if you found this easy to understand!