What is the difference between tokio and async-std

Tokio is a production-grade, multi-threaded runtime optimized for high-performance I/O, while async-std is a single-threaded runtime designed to mimic the standard library's API. Tokio is the industry standard for web servers and complex async applications, whereas async-std is better suited for simpler tasks or when you need strict standard library compatibility.

[dependencies]
tokio = { version = "1", features = ["rt-multi-thread"] }
# OR
async-std = "1.12"

Think of Tokio as a large, busy restaurant with many waiters (threads) handling many tables at once, making it fast for heavy traffic. Async-std is like a single waiter who is very efficient but can only handle one thing at a time. You choose Tokio for big, fast applications and async-std for smaller, simpler tools.