Despite using Tokio underneath, I think that Actix does NOT do work stealing and uses mostly separate threads:

• https://actix.rs/docs/server/#multi-threading
• https://docs.rs/actix-rt/latest/actix_rt/

Given this architecture, I think the article might inaccurate when it says that Actix handlers must be Send + Sync. See also: https://www.reddit.com/r/rust/comments/14cbe1u/why_does_actixwebs_handler_not_require_send/

Actix is a bit weird, but it has been around, and used in production, for a relatively long time.