Looks very nice from the ergonomics point of view. Trying to figure out the "call stack" of a bunch of Actors communicating via promises and futures is a mess (

Looks very nice from the ergonomics point of view. Trying to figure out the "call stack" of a bunch of Actors communicating via promises and futures is a mess (the physical call stack doesn't match the logical one at all) and their solution looks great. Also great work on making Swift and C++ seemingly so interoperable--I didn't know that was possible. I wish they talked about performance. FoundationDB has a lot of low-level optimizations to make the overhead for the concurrency primitives low, custom arena-based allocators, etc. Given that C++ is often chosen for systems code because of potential for low performance overhead, it would have been interesting to see some benchmarks of how well the new Swift code performs compared to the Flow/C++ code.