async/await with tokio for concurrent I/O without blocking threads

Rust's async/await syntax lets you write asynchronous code that looks synchronous. An async fn returns a Future, which is a lazy computation. Calling .await yields control until the future is ready, allowing other tasks to run. Tokio is the most popular async runtime; it provides a scheduler, timers, and async I/O primitives. The key is that async is zero-cost: futures compile to state machines, and there's no heap allocation per task. I use async for network servers, database clients, and any I/O-heavy workload. The ergonomics are similar to Go or Node.js, but with Rust's safety guarantees. The catch is that async Rust has a steeper learning curve (lifetimes in futures, Send bounds), but it's worth it for high-performance services.