Node.js is a JavaScript runtime built on Chrome’s V8 engine. It uses a single-threaded, event-driven, non-blocking I/O model to handle multiple requests efficiently.
V8 Engine
Executes JavaScript by compiling it into machine code
Provides fast performance
Event Loop
Central mechanism that processes asynchronous tasks
Runs on a single thread
Executes callbacks when operations complete
Libuv
Handles asynchronous I/O operations
Manages the event loop and internal thread pool
Thread Pool
Used for heavy I/O tasks (file system, crypto, DNS)
Prevents blocking the event loop
Operations are executed asynchronously
Node.js continues processing other tasks
Results are handled via callbacks, promises, or async/await
Client sends request
Event loop receives it
I/O tasks handled by libuv
Callback placed in queue
Event loop executes callback
Response sent to client
Single-threaded execution
High concurrency
Low memory usage
Fast performance
Not suitable for CPU-intensive tasks
Single thread can block execution
Solutions: Worker Threads, Clustering
Web APIs
Real-time applications
Microservices
Streaming apps
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