What is rate limiting and how can it be implemented?

Rate limiting is a mechanism to restrict the number of requests a client can send to a server within a certain period of time. It helps protect the server from overloads and abuse.

Implementation can be on the server side or the client side. On the frontend, simple protections are often implemented, such as blocking repeated button presses or limiting the frequency of API calls.

An example of a simple implementation in JavaScript using a timer:

let lastRequestTime = 0;
const RATE_LIMIT_INTERVAL = 1000; // 1 second

function sendRequest() {
  const now = Date.now();
  if (now - lastRequestTime < RATE_LIMIT_INTERVAL) {
    console.log('Too frequent! Please wait a bit.');
    return;
  }
  lastRequestTime = now;
  // send request
  fetch('/api/data')
    .then(response => response.json())
    .then(data => console.log(data));
}

For more complex cases, libraries are used or rate limiting is implemented on the server using Redis, tokens, or counters.