[[Node.js-Backend-Architecture]]
📌 Brief Summary
Node.js backend architecture refers to the structural design of server-side applications leveraging the V8 engine's event-driven, non-blocking I/ and single-threaded event loop model. It focuses on optimizing scalability and throughput by managing asynchronous operations through a decoupled, modular approach to handle high concurrency.

📖 Core Content
*   **Event-Driven Non-Blocking I/O Model**: The core of Node.js architecture is the Event Loop, which manages asynchronous operations. Unlike multi-threaded architectures that spawn a new thread per request (leading to high memory overhead), Node.js utilizes a single-threaded loop to delegate I/O tasks (network, file system, database) to the system kernel or a worker pool (libuv). This allows the main thread to remain responsive to new incoming requests while waiting for I/O completion.
*   **Architectural Patterns**:
    *   **Layered Architecture (N-Tier)**: The most common approach in professional Node.js development, separating concerns into Controller (routing/request parsing), Service (business logic), and Data Access/Repository (database interaction) layers. This separation is critical for implementing robust TypeScript interfaces.
    *   **Microservices Architecture**: Leveraging Node.js's lightweight nature to decompose monolithic applications into small, independent services communicating via REST, gRPC, or Message Brokers (RabbitMQ/Kafka). This facilitates independent scaling and fault isolation.
    *   **Hexagonal Architecture (Ports and Adapters)**: A sophisticated pattern used to decouple the core business logic from external dependencies (databases, APIs, UIs). In a TypeScript context, this relies heavily on defining strict interfaces for "Ports" to ensure the domain model remains agnostic of infrastructure implementation.
*   **Concurrency Management via Worker Threads**: While the event loop handles I/O-bound tasks, CPU-intensive tasks (e.g., heavy computation, image processing) are offloaded to `worker_threads`. This prevents the event loop from blocking, maintaining the application's high-availability characteristics.
*   **Data Flow and Middleware**: The architecture heavily utilizes a middleware pipeline (e.g., Express/Fastify middleware pattern). Each request passes through a series of functions that can modify the request object, perform authentication, or handle error propagation, necessitating well-defined Type Guards and Interface definitions to maintain type safety across the pipeline.

🔗 Knowledge Connections
* Related Topics: [[Dependency-Injection-in-TypeScript]], [[Domain-Driven-Design-Interface-Modeling]]
* Projects/Contexts: [[Enterprise-Scale-Microservices]]
* Contradictions/Notes: While the single-threaded nature is an advantage for I/O, it creates a bottleneck for CPU-bound tasks; therefore, architectural decisions must distinguish between I/O-intensive and CPU-intensive workloads.

Last updated: 2026-04-17