CraftComposable · Yields to: Voice, Process

Harden

Production-harden code for 1M+ users. Adds caching, rate limiting, graceful shutdown, error handling, and scalability patterns.

When to Use

• User says "harden my code", "prepare for launch", "make it scalable"
• Code needs caching, rate limiting, or error handling
• Preparing for high traffic

Triggers

"harden my code", "prepare for launch", "add caching",
"add rate limiting", "make it production-ready"

Examples

Example 1

Harden an API endpoint

Add production patterns to a simple Express endpoint.

Before:

app.get('/api/users/:id', async (req, res) => {
  const user = await db.findUser(req.params.id);
  res.json(user);
});

After /harden:

const rateLimit = require('express-rate-limit');
const cache = new NodeCache({ stdTTL: 60 });

const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 });

app.get('/api/users/:id', limiter, async (req, res) => {
  const cacheKey = `user:${req.params.id}`;
  const cached = cache.get(cacheKey);
  if (cached) return res.json(cached);

  try {
    const user = await db.findUser(req.params.id);
    if (!user) return res.status(404).json({ error: 'User not found' });
    cache.set(cacheKey, user);
    res.json(user);
  } catch (err) {
    logger.error('User fetch failed', { id: req.params.id, err });
    res.status(500).json({ error: 'Internal server error' });
  }
});

Example 2

Refactor then harden

Clean up messy code, then add production patterns.

/refactor → /harden

Refactor splits a 2000-line monolith into focused modules.
Harden adds: rate limiting per module, graceful shutdown
handlers, health check endpoints, structured logging,
input validation, and error boundaries.

What It Adds

Pattern	Description
Caching	In-memory, Redis, CDN, cache invalidation
Rate Limiting	Token bucket, sliding window, per-user limits
Graceful Shutdown	Signal handling, connection draining, cleanup
Error Handling	Retry logic, circuit breakers, fallbacks
Monitoring	Health checks, metrics, logging
Security	Input validation, CORS, CSP, auth