Async programming is Python's most powerful yet misunderstood feature. Here is how to build a production-ready async crawler.
The Performance Gap
Fetching 100 URLs (1 second each):
- Synchronous: ~100 seconds
- Asynchronous: ~2-3 seconds
That is 30-50x faster with the same hardware.
Key Patterns
Features of Production Crawler
- Concurrency control with semaphores
- Automatic retries with exponential backoff
- SQLite persistence
- Progress monitoring
Full code includes 200+ lines with AsyncCrawler class, metrics collection, and graceful shutdown.
Complete code on my blog
