Cats Effect 3
summary
Cats Effect 3 presents a ground-up IO implementation with a redesigned typeclass hierarchy (spawn, concurrent, temporal, sync, async), built-in fromCompletableFuture and blocking/interruptible primitives, an execution context users can summon, and a new dispatcher for safe callbacks. The runtime claims zero allocations during interpretation, fiber-aware schedulers, and big real-world gains: a high-contention scatter/gather benchmark shows 55x faster than a fixed thread pool, a JSON-style heat test ~2x, and an fs2/netty echo server within ~12–15% of tuned raw Netty.
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chapters (9)
- 0:00Introduction to Cats Effect 3
- 1:10Design philosophy and goals
- 3:56Evolution from Cats Effect 2
- 7:46User experience improvements
- 12:02New core calculus explained
- 17:35Type class hierarchy breakdown
- 23:51IO implementation details
- 29:26Performance benchmarks results
- 38:08Ecosystem and release plans
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