-1: Single-threaded Node.js does not create a new thread for each client connection, but uses only one thread. When a user connects, an internal event is triggered, making Node.js programs macroscopically parallel through non-blocking I/O, event-driven mechanisms. With Node.js, a server with 8GB of ram, it can handle connections from over 40,000 users at the same time. In addition, the benefit of single threading is that the operating system completely eliminates the time overhead of thread creation and destruction. The downside is that one user crashes the thread, the entire service crashes, and everyone else crashes. -2: Non-blocking I/O Node.js uses the non-blocking I/O mechanism. Therefore, after executing the code that accesses the database, it immediately executes the following code and puts the code that returns the database result into the callback function, thus improving the execution efficiency of the program. -3: An event-driven event mechanism. The event loop, whether a new user's request or an old user's I/O is completed, will be added to the event loop in the form of an event and wait for schedulingCopy the code