What key aspects or skills in Node.js do you feel are not sufficiently mastered?

One of the often underestimated areas in Node.js is a deep understanding of the asynchronous model and the event loop. Many developers know that Node.js operates asynchronously, but do not always understand how callbacks, promises, and microtasks are processed, which can lead to errors and suboptimal code.

It is also important to pay more attention to memory management and profiling of applications, as memory leaks in long-running Node.js processes can be unnoticed without special tools.

Skills with streams and buffers often remain at a basic level, although they are critical for efficient processing of large volumes of data.

Example: correct use of streams for reading a file and sending it over HTTP without loading the entire file into memory:

const fs = require('fs');
const http = require('http');

http.createServer((req, res) => {
  const stream = fs.createReadStream('largefile.txt');
  stream.pipe(res);
}).listen(3000);

It is also important to understand the security of Node.js applications, including protection against injections, CORS configuration, and secure storage of secrets.