Currently, Hydro is focused on networked applications, where most parallelism is across machines rather than within them. So there is some extra overhead if you want single-machine parallelism. It's something we definitely want to address in the future, via shared memory as you mentioned.

At POPL 2025 (last week!), an undergraduate working on Hydro presented a compiler that automatically compiles blocks of async-await code into Hydro dataflow. You can check out that (WIP, undocumented) compiler here: https://github.com/hydro-project/HydraulicLift