InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now. Learn more →
Top 17 Scala Reactive Projects
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Akka
A platform to build and run apps that are elastic, agile, and resilient. SDK, libraries, and hosted environments.
Project mention: Byte Buddy is a code generation and manipulation library for Java | news.ycombinator.com | 2025-08-08> The better question is why use Java for anything these days.
Java (the language) is pretty much "C for the JVM." By that, I mean frameworks/libraries intended for maximum potential use in languages running on the JVM (such as Kotlin, Scala, and of course Java) all support Java (the language) interoperability. Many written in alternate languages targeting the JVM, such as Akka[0], typically have some degree of Java (the language) support as well.
While I prefer to program in one of the alternate programming languages targeting the JVM, I understand why many OSS projects are implemented in Java (the language) for the reasons outlined above.
0 - https://github.com/akka/akka
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Stream
Stream - Scalable APIs for Chat, Feeds, Moderation, & Video. Stream helps developers build engaging apps that scale to millions with performant and flexible Chat, Feeds, Moderation, and Video APIs and SDKs powered by a global edge network and enterprise-grade infrastructure.
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~/project$ sbt run [info] welcome to sbt 1.10.6 (Ubuntu Java 17.0.14) [info] loading settings for project scala-api-heroku-build from plugins.sbt... [info] loading project definition from /home/alvin/repositories/devspotlight/heroku/scala/scala-api-heroku/project [info] loading settings for project root from build.sbt... [info] loading settings for project docs from build.sbt... [info] __ __ [info] \ \ ____ / /____ _ __ __ [info] \ \ / __ \ / // __ `// / / / [info] / / / /_/ // // /_/ // /_/ / [info] /_/ / .___//_/ \__,_/ \__, / [info] /_/ /____/ [info] [info] Version 3.0.6 running Java 17.0.14 [info] [info] Play is run entirely by the community. Please consider contributing and/or donating: [info] https://www.playframework.com/sponsors [info] --- (Running the application, auto-reloading is enabled) --- INFO p.c.s.PekkoHttpServer - Listening for HTTP on /[0:0:0:0:0:0:0:0]:9000 (Server started, use Enter to stop and go back to the console...)
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pekko
Build highly concurrent, distributed, and resilient message-driven applications using Java/Scala
Project mention: Hydro: Distributed Programming Framework for Rust | news.ycombinator.com | 2025-01-31Seems like it based on GH activity, but I don’t know for sure.
https://github.com/apache/pekko
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Reactive-kafka
Alpakka Kafka connector - Alpakka is a Reactive Enterprise Integration library for Java and Scala, based on Reactive Streams and Akka.
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alpakka
Alpakka is a Reactive Enterprise Integration library for Java and Scala, based on Reactive Streams and Akka.
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InfluxDB
InfluxDB – Built for High-Performance Time Series Workloads. InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now.
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AkkaGRPC
A platform to build and run apps that are elastic, agile, and resilient. SDK, libraries, and hosted environments.
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SaaSHub
SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives
NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020).
Scala Reactive discussion
Scala Reactive related posts
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Play Framework – Build Modern and Scalable Web Apps with Java and Scala
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Play Framework 2.9.0 Release Candidate
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Play (1) Linux manual page
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Scala opensource projects
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Play Framework for Java and Scala
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How does web developement process compare to java web developement ?
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Kalix: Move to the Cloud. Extend to the Edge. Go Beyond.
- A note from our sponsor - InfluxDB www.influxdata.com | 22 Dec 2025
Index
What are some of the best open-source Reactive projects in Scala? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | Akka | 13,242 |
| 2 | Play | 12,614 |
| 3 | Lagom | 2,630 |
| 4 | pekko | 1,505 |
| 5 | Reactive-kafka | 1,419 |
| 6 | Akka HTTP | 1,346 |
| 7 | alpakka | 1,269 |
| 8 | Phantom | 1,045 |
| 9 | ReactiveMongo | 851 |
| 10 | topshell | 479 |
| 11 | OutWatch | 469 |
| 12 | AkkaGRPC | 433 |
| 13 | aecor | 326 |
| 14 | Pulsar4s | 232 |
| 15 | Play WS | 224 |
| 16 | lila-ws | 169 |
| 17 | Clickhouse-scala-client | 119 |
Sponsored
Stream - Scalable APIs for Chat, Feeds, Moderation, & Video.
Stream helps developers build engaging apps that scale to millions with performant and flexible Chat, Feeds, Moderation, and Video APIs and SDKs powered by a global edge network and enterprise-grade infrastructure.
getstream.io