Why This Matters

Extensions often call external APIs (internal services, third-party). Reliable API integration is essential for Extension quality.

Concept Explained

API client design: typed responses, error handling, retries, caching. Use when Extension needs live data from external service.

How It Works

Build typed API client. Handle errors (timeouts, 4xx, 5xx). Retry with backoff. Cache responses to reduce latency and cost.

Step-by-Step Tutorial

1. Build API client

2. Handle errors

3. Retry with backoff

4. Cache responses

5. Log and monitor

Real-World Example

A team's Extension called an internal service that was occasionally slow. Without retries, Extension failed on slow responses. Added 3 retries with backoff. Failure rate dropped from 5% to 0.1%.

Example Prompts / Commands / Code

"""const NodeCache = require('node-cache');
const cache = new NodeCache({ stdTTL: 60 }); // 1 min cache

async function callService(path, options = {}) {
  const cacheKey = `${path}:${JSON.stringify(options)}`;
  const cached = cache.get(cacheKey);
  if (cached) return cached;

  for (let attempt = 0; attempt < 3; attempt++) {
    try {
      const response = await fetch(`https://internal-service.corp${path}`, options);
      if (response.status >= 500) {
        throw new Error(`Server error: ${response.status}`);
      }
      if (response.status >= 400) {
        throw new Error(`Client error: ${response.status}`); // don't retry
      }
      const data = await response.json();
      cache.set(cacheKey, data);
      return data;
    } catch (error) {
      if (attempt < 2) {
        await new Promise(r => setTimeout(r, 1000 * 2 ** attempt));
        continue;
      }
      throw error;
    }
  }
}
"""

Common Mistakes

• No error handling — Extension breaks on API failure.
• Retrying 4xx errors — wastes resources (won't succeed).
• No caching — excessive API calls, slow responses.
• Not monitoring API health — silent failures.

Best Practices

• Build typed API client.
• Handle errors: retry 5xx, don't retry 4xx.
• Max 3 retries with exponential backoff.
• Cache responses (TTL-based).
• Log and monitor API call health.

Troubleshooting

Practical Exercise

Professional Challenge

Frequently Asked Questions

Further Reading

• Building Extensions

Official References

• Building Extensions

Related lessons: PR-24, PR-25