Does the Rust actors framework Actix guarantee message order between two actors?

Question

In the case of one single actor sending a message to another single actor.

I couldn't find anything about this in the official documentation.

Answer 1

The order in which messages are received from one single actor to another single actor is deterministic:

Order is deterministic. Actix uses mpsc queue for messages

See the answer from the author in the rust subreddit.