• Answer: Node.js is an open-source, cross-platform JavaScript runtime built on Chrome’s V8 engine. It enables JavaScript to be used outside of a browser, allowing developers to build server-side applications. Unlike traditional server environments, Node.js uses an event-driven, non-blocking I/O model, which is highly efficient for building scalable applications. It’s particularly well-suited for real-time applications like chat servers or collaborative tools.

Event-Driven and Asynchronous Model

• One of the defining features of Node.js is its event-driven and asynchronous architecture:
  • Event-Driven: Node.js uses an event loop to handle incoming requests and execute tasks when an event occurs (like an HTTP request or file read). This approach allows Node.js to manage tasks without waiting for each task to complete sequentially.
  • Asynchronous I/O: Unlike traditional synchronous I/O, where each task must complete before the next one begins, Node.js allows I/O operations (file reading, HTTP requests, etc.) to run in the background. This way, the main execution thread is free to handle additional tasks, resulting in non-blocking, efficient code execution.

Single-Threaded Yet Scalable

• Node.js operates on a single-threaded event loop, which might sound limiting compared to multi-threaded server environments like Java or .NET. However, due to its non-blocking, asynchronous nature, Node.js can efficiently manage a large number of simultaneous connections without creating multiple threads for each connection.
• For I/O-heavy tasks like reading from databases or handling network requests, Node.js can be incredibly efficient. However, for CPU-intensive tasks, which require heavy computation, Node.js is less efficient. To address this, Node.js allows developers to spawn child processes or leverage the worker threads module to handle such tasks without blocking the main thread.

Non-Blocking I/O Operations

• The non-blocking I/O model in Node.js is a key part of its efficiency. When performing tasks like reading files, querying databases, or calling APIs, Node.js initiates these tasks and moves on to the next one without waiting for the current one to complete. It will only act on the result of the task when the data is ready.
• For example, if a Node.js server is handling a file read request, it can begin processing the file but immediately move on to handle other requests. When the file data is ready, the server will receive a notification and proceed with the next steps, allowing a more efficient use of server resources.