Authentication Use Cases

Use Cases Overview

At its core, use cases is about doing one thing well inside your authentication project. Once you understand the pattern, you can apply it consistently across features and teams.

Good use cases pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

import express from 'express';
import jwt from 'jsonwebtoken';

const app = express();
app.use(express.json());

function authenticate(req, res, next) {
  const token = req.headers.authorization?.replace('Bearer ', '');
  try {
    req.user = jwt.verify(token, process.env.JWT_SECRET);
    next();
  } catch {
    res.status(401).json({ error: 'Unauthorized' });
  }
}

Authentication middleware verifies the caller's identity before protected handlers run.

Use Cases Example

// verify the caller on every protected request
function authenticate(req, res, next) {
  const token = req.headers.authorization?.replace('Bearer ', '');
  req.user = verifyToken(token); // throws if invalid
  next();
}

• Start from a minimal Use Cases example and grow it only as needed.
• Keep configuration explicit so Use Cases behaves the same in every environment.
• Name things clearly so teammates understand your Use Cases at a glance.
• Add tests around Use Cases early to lock in expected behaviour.

Authentication Cheatsheet

Quick authentication reference related to use cases.

How Use Cases Works

Use Cases is part of proving who a user is and what they are allowed to do. Authentication verifies identity, while authorization decides access — and use cases plays a specific role in that flow.

Authentication middleware verifies the caller's identity before protected handlers run.

• Never store or log plain-text passwords or secrets.
• Prefer short-lived tokens with refresh over long-lived ones.
• Always send credentials over HTTPS.
• Fail closed: deny access when anything is uncertain.

Security Guidance for Use Cases

Security is the whole point of use cases. Small mistakes — weak hashing, tokens in localStorage, missing rate limits — are exactly what attackers look for, so follow proven defaults.

Common Mistakes

• Copying use cases snippets without understanding what each line does.
• Skipping error handling and edge cases when wiring up use cases.
• Leaving use cases untested, so regressions slip into production.
• Over-engineering use cases before you actually need the extra flexibility.

Key Takeaways

• Use Cases is a core part of working effectively with authentication.
• Start small and keep use cases focused on a single responsibility.
• Apply consistent patterns so use cases scales across your project.
• Test and document use cases to keep it maintainable over time.