How Does Async Work in Code?

The exact mechanics vary between programming languages, but many modern languages provide the familiar async and await keywords to make asynchronous code easier to write and reason about.

At a conceptual level, async identifies code that participates in asynchronous execution, while await marks a point where that code depends on the result of an asynchronous operation.

If that result is already available, execution may simply continue. If it isn’t, the function can yield rather than blocking there, allowing other work to make progress. Once the awaited operation completes, execution can continue from that point.

You can think of await as saying: “I need the result of this operation before I can continue from here, but there’s no reason to block everything else while I’m waiting for it.”

The precise details of what happens underneath, whether that involves an event loop, tasks, promises, futures, state machines or something else, depend on the language and runtime. But you don’t need to understand all of those implementation details to understand the basic async mental model.