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akka-streams

🎯Skill

from alexandru/skills

What it does

Enables reactive dataflow programming in Scala using Akka and Pekko Streams, with emphasis on testable components and selective stream usage.

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Part of

alexandru/skills(8 items)

akka-streams

Installation

Quick InstallInstall with npx

npx skills add https://github.com/alexandru/skills --skill <skill-name>

📖 Extracted from docs: alexandru/skills

Need more details? View full documentation on GitHub →

2Installs

AddedFeb 4, 2026

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Skill Details

SKILL.md

Scala reactive streaming with Akka Streams and Pekko Streams. Use for dataflow and reactive programming patterns, testing stream components, and understanding when NOT to use streams (prefer plain functions for transformations and I/O).

Overview

# Akka Streams and Pekko Streams (Scala)

Quick start

Think twice before using Streams: prefer plain functions, even for I/O.
Test stream components using TestSource, TestSink, and TestProbe from akka-stream-testkit.
Always define supervision strategies for error handling; default behavior tears down the entire stream.
Read references/akka-streams.md for core concepts and patterns.
Read references/best-practices.md for critical guidance on when NOT to use streams.
Read references/testing.md for comprehensive testing examples.

When NOT to use Streams

Don't model plain data transformations as stream operators; use regular functions instead.
Don't use streams for general I/O; prefer plain functions or other abstractions.

Workflow

Verify that Streams are the right tool: do you need dataflow or reactive programming patterns?
Design Source, Flow, and Sink components as separate, testable units.
Define error handling with recover, recoverWithRetries, or supervision strategies.
Test each component with TestSource/TestSink or TestProbe before integration.
Compose the final graph and materialize with explicit error handling.

Testing rules

Write tests using akka-stream-testkit for custom stream components.
Use TestSource.probe and TestSink.probe for fine-grained control over element flow.
Test backpressure behavior explicitly using request() and expectNoMessage().
Test error scenarios with expectError() or supervision strategies.

Pekko Streams

Pekko Streams is a fork of Akka Streams with identical APIs (package names change from akka. to org.apache.pekko.).
All guidance for Akka Streams applies equally to Pekko Streams.
When working with Pekko, adjust imports but keep patterns and testing approaches identical.

Output expectations

Keep stream topologies simple and testable; break complex graphs into named components.
Make error handling explicit via supervision or recovery operators.
Prefer immutability; stream graphs are blueprints until materialized.

References

Load references/akka-streams.md for core concepts, operators, and materialization.
Load references/best-practices.md for critical guidance on avoiding stream overuse.
Load references/testing.md for testing patterns and complete examples.

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