cff

Sourcegraph Conc is broadly similar in providing pool helpers, but doesn't provide the same fine grained batching options: https://github.com/sourcegraph/conc Uber CFF does code generation, and has more of a focus on readability and complex dependency chains: https://github.com/uber-go/cff

"The amount of APIs in the world that require concurrency within a single request scope to meet latency needs approaches zero." I've never worked on any non-Rails API where this was true. The Ruby community keeps telling me this, but in languages where concurrency is well supported, it gets used everywhere to a great extent. I obviously don't have hard data to support this, but your claim seems pretty far fetched to be honest. "In practice, you don’t make that db call until the auth request is done and the user is verified" Of course you optimistically do any idempotent DB operations while waiting for auth to succeed if you care about latency. "you don’t make the outgoing api call until you already have the results of the db call, because you need your data to form the outgoing request" These dependencies of course exist, but so do parts