We should add an architecture guide page for the async step-down feature describing the API, the motivation behind the design (and what advantages it provides compared with blocked step-down), all restrictions and user requirements, as well as interesting implementation details and notes (such as the concurrency model or why different user requirements exist).

Regarding the concurrency model, this document should also combine both parts of the concurrency model analysis documents that we created for this feature (please see the comments). Additionally, a review of this section by a Staff+ engineer who is considered a concurrency expert on the team is required to ensure that we haven’t missed anything on that front.

We should also check whether introducing a mutex from the second concurrency model analysis document allows us to weaken some of the user-side requirements (for example, the requirement for external mutex synchronization).