server/rateLimiter.js

// Simple sliding window rate limiter
const windows = new Map();

export function rateLimiter(key, maxRequests, windowMs) {
  const now = Date.now();
  if (!windows.has(key)) {
    windows.set(key, { count: 1, resetAt: now + windowMs });
    return true;
  }
  const entry = windows.get(key);
  if (now > entry.resetAt) {
    entry.count = 1;
    entry.resetAt = now + windowMs;
    return true;
  }
  if (entry.count >= maxRequests) return false;
  entry.count++;
  return true;
}

// Cleanup every 5 minutes
setInterval(() => {
  const now = Date.now();
  for (const [k, v] of windows.entries()) {
    if (now > v.resetAt) windows.delete(k);
  }
}, 5 * 60 * 1000);