Python’s asynchronous frameworks, like asyncio, Tornado, and Twisted, are increasingly important for writing high-performance web applications. Even if you’re an experienced web programmer, you may lack a rigorous understanding of how these frameworks work and when to use them. Let’s see how asyncio's event loop works, and learn how to efficiently handle very large numbers of concurrent connections. Attendees will learn when to use async and when not to. They’ll learn about asyncio, a major new feature in the Python 3.4 standard library: what it is, how it works, and how to use it for high-concurrency web programming.