That's kind of wild... I'm relatively novice with Rust still, but I was pretty aware that the different executors weren't the only async option... I thought it was pretty cool you could opt into tokio for the bulk of async request work, but if I wanted to use a pool for specific workers, or something else on a more monolithic service/application, I could still launch my own threads for that use case pretty easily.

The hardest parts for me to grok really came down to lifetime memory management, for example a static/global dictionary as a cache, but being able to evict/recover entries from that dictionary for expired data... This is probably the use case that IMO is one of the least well documented, or at least lacking in discoverable tutorials etc.