What is 'fire-and-forget' async code, and why is it generally discouraged in production Node.js applications?

Fire-and-forget means calling an async function without awaiting or attaching a .catch() to its returned promise -- the calling code moves on immediately without knowing whether the operation succeeded, failed, or is still in progress. This is discouraged because any rejection becomes an unhandled promise rejection (potentially crashing the process on modern Node.js), and because the calling code has no way to guarantee the operation actually completed before, say, the process exits or a response is sent.

// Fire-and-forget: risky, errors are silently unhandled
function handleRequest(req, res) {
  logAnalyticsEvent(req); // not awaited -- if this rejects, it's an unhandled rejection
  res.json({ status: 'ok' });
}

// Safer: explicitly handle the case where you intentionally don't want to block
function handleRequest(req, res) {
  logAnalyticsEvent(req).catch(err => logger.error('Analytics logging failed', err));
  res.json({ status: 'ok' });
}