Event-Driven Architecture (EDA) is a paradigm that enables developers to build responsive and scalable applications, particularly when working with Node.js. By utilizing event-driven programming, developers can create systems that are highly efficient and capable of handling a large number of concurrent connections. In this architecture, components communicate through events, allowing for asynchronous processing of information. This is particularly beneficial in web applications where user interactions can trigger a cascade of events, making the application more responsive and user-friendly.

One of the key advantages of EDA in Node.js is its ability to simplify the management of complex workflows. With an event-driven approach, developers can easily decouple their application logic and leverage the Node.js event loop to manage multiple events seamlessly. This leads to improved performance since operations can proceed without waiting for each other to complete. Moreover, event-driven systems often result in better resource utilization, as they enable applications to handle numerous processes efficiently, maximizing throughput and minimizing latency.

When working with asynchronous code in Node.js, developers often encounter pitfalls that can lead to performance issues and bugs. One common mistake is not handling errors appropriately. Failing to catch exceptions in asynchronous functions, particularly when using Promise or async/await, can result in unhandled rejections that crash the application. To mitigate this, always implement error handling using .catch() for promises and try/catch blocks for async functions.

Another frequent oversight is forgetting to return promises in asynchronous functions. When a function initiates asynchronous operations, it’s crucial to return the promise it creates so that the calling code can properly await its resolution or handle its outcome. Not returning a promise can lead to unexpected behaviors and makes debugging more complex. Make it a habit to return promises from your asynchronous functions to maintain predictable behavior in your code.

Node.js is built upon a single-threaded architecture, which means it handles concurrency through an event-driven model. The event loop is essential to Node.js's non-blocking nature, allowing it to process numerous simultaneous connections without requiring multiple threads. Instead of traditional multi-threading, Node.js uses an asynchronous, non-blocking I/O model. This approach enables developers to write applications that can handle many connections concurrently, as the event loop can manage callbacks for operations such as file reading, database querying, and network requests without holding up the execution of other code.

While Node.js excels at concurrency, it does not natively manage parallelism due to its single-threaded architecture. However, it leverages the libuv library to handle I/O operations in the background through worker threads. For CPU-intensive tasks that require parallel execution, developers can utilize the Worker Threads module or third-party libraries such as Cluster to spawn multiple instances of the Node.js application. This multi-process capability allows the system to take full advantage of multi-core processors, providing better performance for applications demanding high concurrency and parallelism.