ZIO
Hacker ApprovedRanked 3 of 11 concurrency libraries by recommenders
Recommended for its ergonomic, typed effects system that makes concurrency and async code more robust and easier to read. One critic calls it all complexity and no guarantees.
Recommended for its ergonomic, typed effects system that makes concurrency and async code more robust and easier to read. One critic calls it all complexity and no guarantees.
13 people gave an opinion
- recommend it
- 11
- criticize it
- 2
- approval share
- 85%
Recommended in 9 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: not recommended
- September 2026: recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 11 people recommend itNeeds 10 or more, met.
- 5.5 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 9 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Typed effects make async robust
“I personally find async runtimes with typed front-ends much more robust and much less error-prone.”
Comment from 14 Mar 2026 in “The Isolation Trap: Erlang” “a mature effects system for a semi-popular language”
Comment from 6 Mar 2026 in “Async Programming Is Just Inject Time” Ergonomic and easy to read
“The primary benefit of concise but robust frameworks like ZIO is that they are easy to read”
Comment from 29 Jan 2026 in “The Sovereign Tech Fund Invests in Scala” “Scala's ZIO also demonstrates that they're a great idea and can be perfectly ergonomic”
Comment from 15 Sep 2026 in “Java 27” “all of which are quite ergonomic”
Comment from 29 Jan 2026 in “The Sovereign Tech Fund Invests in Scala” Automatic context propagation without boilerplate
“In Scala (especially ZIO) propagation is all automatic and you just handle it wherever you'd like.”
Comment from 26 Apr 2026 in “What Async Promised and What It Delivered” “except you don't have to remember to pass around or select on the ctx”
Comment from 7 Mar 2026 in “What canceled my Go context?” Libraries and ecosystem arrive early
“Typelevel and ZIO really put a lot of effort to release many libraries on day 1”
Comment from 30 Nov 2025 in “The Origins of Scala (2009)” “I'd be happy to use just that bit and stick with ZIO/TypeLevel's ecosystem”
Comment from 7 Nov 2025 in “We chose OCaml to write Stategraph”
Other concurrency libraries people recommend
The four most recommended other concurrency libraries, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| Tokio | 57 | 45 | 56% | 12 | — | — |
| Akka | 12 | 9 | 57% | 7 | — | — |
| ZIOThis page | 11 | 2 | 85% | 9 | — | Approved |
| Trio Python library | 10 | 0 | 100% | 8 | — | Approved |
| core.async | 9 | 4 | 69% | 6 | — | — |
What people said
17 of the 19 comments that mention it, newest first. Each links to the original comment.
“it's kind of the worst of both worlds (all the complexity, none of the guarantees)”
“zio (the one I'm working on)”
“Scala's ZIO also demonstrates that they're a great idea and can be perfectly ergonomic”
“It isn't very hard to find folks misusing unsafe to mean something else other than memory safety, or their own ZIO like frameworks.”
“I say this as someone using Scala 3 with ZIO effects system”
“In Scala (especially ZIO) propagation is all automatic and you just handle it wherever you'd like.”
“brings composable concurrency and transactional memory amongst other features”
“It is a big reason why I picked Scala3/Zio over Rust for my most recent project.”
“I personally find async runtimes with typed front-ends much more robust and much less error-prone.”
“except you don't have to remember to pass around or select on the ctx”
“a mature effects system for a semi-popular language”
“all of which are quite ergonomic”
“The primary benefit of concise but robust frameworks like ZIO is that they are easy to read”
“if you use a library, like monix or zio, you dont have to deal with Future”
“Typelevel and ZIO really put a lot of effort to release many libraries on day 1”
“I'd be happy to use just that bit and stick with ZIO/TypeLevel's ecosystem”
“Scala has a far more fragmented ecosystem with Cats, Scalaz, Zio and Akka.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.