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December 19th, 2025, ISSUE 607

READING

Scala 3 slowed us down?

A seemingly smooth Scala 2.13 → 3 migration hid a subtle Quicklens bug that tanked Kafka throughput and spiked CPU, showing how library behavior can drastically change across Scala versions.
Krzysztof Maliszewski
Coroutines, Event Loops - Build Your Own in Scala

Hands-on guide to building your own coroutine and event-loop–based async runtime in Scala 3 using GraalVM continuations, including internals of tasks, scheduler, runtime wiring, and a complete working example.
Chia-Hung Lin
Advent of Code 2025 in Scala (Solutions)

Oto's solutions to all the challenges from 2025.
Oto Brglez (@otobrglez)

VIDEOS

Make delightful web apps with Scala and Krop!

Today we're looking at a new web framework for Scala 3 - krop. It's made by Noel Welsh and it's got some pretty good ideas, so let's see what it's about!
Jakub Kozłowski (@kubukoz)

RELEASES

Apache Pekko 2.0.0-M1

Java 17 is the new minimum, Scala 2.12 support dropped, big change for all Java DSL users, new pekko-serialization-jackson3, a lot of deprecated code removed.
Pekko contributors
baku

A Scala Tapir extension to cleanly decouple API definitions from server and security logic.
arkida39
lohika 0.11.0

Lohika is a proof generator for entailments and tautologies in first-order logic. It now excludes irrelevant steps from the output.
Melvic Ybanez
Scala 2.12.21

This release brings JDK 25 LTS support to the 2.12 series.
Scala contributors
scala-maven-central-pgp-key-bootstrap

Tiny script which generates and uploads PGP key.
Windymelt (@windymelt)
IntelliJ Scala Plugin 2025.3 Is Out!

Support for the upcoming Scala 3.8 release, improves handling of macros, export aliases, extension methods, and type lambdas, introduces Structural Search and Replace for Scala, extends X-Ray mode to Mill build scripts with type parameter visualization, plus many bugfixes.
JetBrains (@jetbrains)

EVENTS

Scalar, Mar 26th - 27th, 2026, Warsaw, Poland

Join Scalar Conference 2026 and prepare for two exciting days of learning about functional programming with a fantastic community!
SoftwareMill (@softwaremill)

VARIA

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