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Top 23 Scala Open-Source Projects
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Feature transformations should be deterministic: The same input should produce the same output when the same feature definition and configuration are applied. This is what allows training, backtesting, and live inference to remain aligned. Tools such as Pandas, Spark, or feature platforms such as Feast can be used to implement that logic.
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Kafka is a distributed streaming platform used to build real-time data pipelines and streaming applications. It allows producers to send messages to topics, which are then consumed by various consumers, making it ideal for event-driven architectures.
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Project mention: Performance Test: Flink 1.19 vs. Spark 4.0 vs. Kafka Streams 3.8 Windowed Aggregation Throughput | dev.to | 2026-05-04
Solution & Implementation: Migrated windowed aggregation from Kafka Streams 3.7 to Flink 1.19, reusing existing Kafka sources/sinks. Optimized Flink config: set parallelism to 16 (matching vCPU), enabled RocksDB state backend with 100ms watermark out-of-order tolerance, configured 5s checkpoints. Trained team on Flink watermarking and state management via Apache Flink GitHub repo documentation.
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Project mention: Lichess and Take Take Take Sign Cooperation Agreement | news.ycombinator.com | 2026-04-09
Lichess is incredibly well optimized [0] (and an amazing public service). I'm sure that this is very cost effective for TTT, so a win-win.
[0] https://lichess.org/@/revoof/blog/optimizing-the-tablebase-s...
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scala
Scala 2 compiler and standard library. Scala 2 bugs at https://github.com/scala/bug; Scala 3 at https://github.com/scala/scala3
The goal of fp-ts is to empower developers to write pure FP apps and libraries built atop higher order abstractions. It includes the most popular data types, type classes, and abstractions from languages like Haskell, PureScript, and Scala.
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Deeplearning4j
Suite of tools for deploying and training deep learning models using the JVM. Highlights include model import for keras, tensorflow, and onnx/pytorch, a modular and tiny c++ library for running math code and a java based math library on top of the core c++ library. Also includes samediff: a pytorch/tensorflow like library for running deep learn...
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During my career break that I started in 2025, I started exploring the ever-changing Generative AI landscape. In Decemember, I was exploring Spring Boot as I hadn't used it in anger professionally having used other Java frameworks like Jersey, Play and I wanted to build something.
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milewski-ctfp-pdf
Bartosz Milewski's 'Category Theory for Programmers' unofficial PDF and LaTeX source
The author has a series of blog posts introducing category theory to programmers: https://bartoszmilewski.com/2014/10/28/category-theory-for-p...
I'll admit to only having read the first few chapters, but it came across as an approachable intro to the math.
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awesomo
Cool open source projects. Choose your project and get involved in Open Source development now.
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Gitbucket
A Git platform powered by Scala with easy installation, high extensibility & GitHub API compatibility
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And in that world, Gatling has a clear edge.
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Zeppelin
Web-based notebook that enables data-driven, interactive data analytics and collaborative documents with SQL, Scala and more.
Project mention: Woxi: Wolfram Mathematica Reimplementation in Rust | news.ycombinator.com | 2026-02-25I wonder if it would make a good Zeppelin interpreter. https://zeppelin.apache.org/
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Doesn't execute notebooks. Pair with nbval or papermill for kernel-level validation.
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> It's kind of like the small string optimization you see in C++ ...
Agreed. These types of optimizations can yield significant benefits and are often employed in language standard libraries. For example, the Scala standard library employs an analogous optimization in their Set[0] collection type.
0 - https://github.com/scala/scala3/blob/88438e2c6e6204e12666067...
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Is this reasoning, or measurement? If measurement, push it to a deterministic tool. Sonar, Spotless, Ruff, ESLint, coverage gates, pre-commit hooks, complexity calculators. Write a script if no tool exists. That's how just lint got built, and that's the Unix-philosophy move for agentic coding. Hooks fire on tool calls; CI fires on PRs; pre-commit fires on commit. Pick the cheapest layer that catches the failure and run it there.
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> to see how they ended up in that situation
The "how" is almost always lack of discipline (or as I sometimes couch it, "imagination") but usually shit like https://github.com/microsoft/SynapseML/issues/405#:~:text=cl...
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With this, you can jump to definitions with M-. and return with M-,, and it also points out indentation issues. For other features, please see the lsp-mode documentation.
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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 discussion
Scala related posts
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Building Kafka Producer-Consumer Using Go and Docker
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Encrypting PostgreSQL Columns in Scala with skunk-crypt
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7 Free Tools for Data Pipeline Reconciliation and Cross-Source Validation
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How to Build a Dead Letter Queue System for Reliable Data Processing
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Idempotency in Data Pipelines: How to Prevent Duplicate Records
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Performance Test: Flink 1.19 vs. Spark 4.0 vs. Kafka Streams 3.8 Windowed Aggregation Throughput
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The Postmortem of a 20-Minute Kafka 3.8 Outage That Delayed 1M Order Messages
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A note from our sponsor - SaaSHub
www.saashub.com | 15 Jun 2026
Index
What are some of the best open-source Scala projects? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | Apache Spark | 43,440 |
| 2 | Apache Kafka | 32,807 |
| 3 | Apache Flink | 26,068 |
| 4 | lila | 18,350 |
| 5 | scala | 14,507 |
| 6 | Deeplearning4j | 14,235 |
| 7 | Play | 12,617 |
| 8 | kafka-manager | 11,938 |
| 9 | milewski-ctfp-pdf | 11,631 |
| 10 | mal | 10,663 |
| 11 | awesomo | 9,860 |
| 12 | Gitbucket | 9,371 |
| 13 | awesome-scala | 9,224 |
| 14 | Finagle | 8,868 |
| 15 | Gatling | 6,923 |
| 16 | Zeppelin | 6,630 |
| 17 | papermill | 6,448 |
| 18 | dotty | 6,256 |
| 19 | spotless | 5,510 |
| 20 | SynapseML | 5,229 |
| 21 | lsp-mode | 5,096 |
| 22 | sbt | 4,927 |
| 23 | Scala.js | 4,702 |
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