I'm on my way back from RustConf. At the Unconf, we had a productive discussion about debugging and benchmarking async applications. Many interesting insights were shared. I'm attempting to enumerate some of them here, along with some of my own experiences. This is the first draft of what I hope can become a living document of best practices. Feel free to file an issue or open a PR . I'm hoping to also add a sample app in the coming days demonstrating these issues along with what the dial9 trace looks like. — Russell There are few hard-and-fast rules for writing code that performs well on Tokio runtimes; the answer to so many questions is "it depends." The performance of a workload depends on what else is running on the runtime at that moment. This is why so many problems only show up in production! Writing async applications that perform well is a balance between fairness and batching, contention and isolation. This post lays out some general principles and covers exceptions where I can.…