Haxl is a great Haskell library and probably the biggest contribution to getting Haskell out of the academia. It is optimized for fetching querying and caching data sources, among other things, making use of parallelism and concurrency while maintaining a level close to the domain problem.

Haxl uses a controlling thread that spawn worker threads and is single purpose. No distributed computing in the strong sense.

transient has no controlling thread. It run multiple threads and is general purpose.

The alternative operator <|> can spawn parallel threads/or parallel distributed computations that follow the flow of the monad. for example:

    r <-   runAt node1 foo <|>  runAt node2 bar
    lliftIO $ print r

will print two results, since there are two thread generated. Well there may be any number of results because any of the two branches may generate multiple threads or none, since they can stop without any result.

(if we need a single thread, we can use `collect`)

note that `foo` and `bar` are distributed programs as well, so they can invoke other nodes and so on.