What do V8, libuv and the thread pool do?

Definition:

V8 is the engine that executes JavaScript, while libuv provides the event loop and cross-platform I/O support. The libuv thread pool runs certain operations that would otherwise block, such as many file-system calls. These are separate roles: V8 does not itself manage every network request, and not every async call uses a pool thread.

Key points:

• V8 runs JavaScript and manages JavaScript memory.

• libuv supports the event loop and asynchronous I/O.

• Its worker pool handles work such as many file operations and some crypto; network I/O usually uses OS readiness notifications.

• Pool saturation can delay unrelated operations that share the pool; inspect the workload before increasing its size.

Interview point:

• Distinguish the JavaScript thread, OS-managed network I/O, libuv pool threads and application worker threads.