Fix Session Error in NestJS

Session Errors in NestJS: What Goes Wrong

Session errors strike when your application tries to read session data that's expired, corrupted, or was never set. In NestJS apps, this often leads to authentication failures or unexpected logouts.

Root Causes

• Session TTL expired between requests
• Server-side session store restarted or cleared
• Cookie domain/path misconfiguration
• Missing session middleware or initialization

Fixing the Problem

// Bad: assuming session always exists
async function getProfile(req: Request) {
  const userId = req.session.userId; // undefined!
  return db.users.findUnique({ where: { id: userId } });
}

// Good: validate session first
async function getProfile(req: Request) {
  if (!req.session?.userId) {
    throw new UnauthorizedException("Session expired");
  }
  return db.users.findUnique({ where: { id: req.session.userId } });
}

Best Practices

1. Always check for session existence before accessing values
2. Implement session refresh logic for long-lived applications
3. Use secure, httpOnly cookies for session identifiers
4. Set appropriate TTL values — not too short, not too long

Track Session Issues with Bugsly

Session bugs are intermittent and user-specific, making them a nightmare to debug. [Bugsly](https://bugsly.io) groups session-related errors by user context and shows you exactly when and why sessions fail — complete with request timelines.