Await promises inside try/catch and never leave a promise unhandled. An unhandled rejection can crash the process or silently drop a failure.
Unhandled promise rejections terminate Node processes and bypass error boundaries, causing silent failures or crashes.
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Errors thrown in async code are not caught by a surrounding synchronous try unless you await inside it. A "floating" promise (called without await or .catch) escapes all handling and surfaces as an unhandledRejection. Always await within the guarded block, or attach a rejection handler.
// Bad — rejection escapes the try entirely
try {
sendEmail(user); // not awaited
} catch (err) { /* never runs */ }
// Good — await inside try; or handle explicitly
try {
await sendEmail(user);
} catch (err) {
logger.error({ err, userId: user.id }, "email_failed");
}