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Kafka Streams

kafka.apache.org

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Spec score 7.9 #15 of 26 in Stream Analytics Software

What it is

Kafka Streams is a free client library for building applications and microservices that use data stored in Kafka clusters. It processes Kafka data with event-time handling, windowing, and real-time queries of application state. The Streams DSL provides operations such as mapping, filtering, joins, and aggregations, while the Processor API supports custom processors and state stores. Fault-tolerant local state supports stateful work such as windowed joins and aggregations, and the library offers exactly-once processing semantics. Applications can run on one machine or scale across multiple machines, and can be deployed in containers, virtual machines, on bare metal, or in cloud environments. Kafka Streams uses Kafka as its internal messaging layer and does not require a separate processing cluster. It supports Java and Scala and integrates with Kafka security features for encryption in transit, client authentication, and authorization. The software is licensed under Apache License 2.0. The Apache Software Foundation says it does not sell its software or provide formal or commercial support for its packages; project communication is available through community mailing lists.

Spec sheet

Purpose
Kafka Streams is a client library for building applications and microservices whose input and output data are stored in Kafka clusters.Read 30 Sep 2026 · kafka.apache.org
Deployment
Kafka Streams applications can be deployed to containers, virtual machines, bare metal, or cloud environments.Read 30 Sep 2026 · kafka.apache.org
Integrations
Kafka's ecosystem includes tools for stream processing, Hadoop integration, monitoring, and deployment, and Kafka Connect provides connectors for external systems.Read 30 Sep 2026 · kafka.apache.org
Security
Kafka Streams natively integrates with Kafka security features, including encryption in transit, client authentication, and client authorization.Read 30 Sep 2026 · kafka.apache.org
Support
The Kafka project provides user, developer, JIRA, and commit mailing lists for community support and project communication.Read 30 Sep 2026 · kafka.apache.org
License
Apache Software Foundation software is licensed under the Apache License 2.0.Read 30 Sep 2026 · apache.org
Founded
1999Read 28 Sep 2026 · kafka.apache.org
APIs
The Streams DSL provides operations such as map, filter, join, and aggregations, while the Processor API supports custom processors and state stores.Read 30 Sep 2026 · kafka.apache.org
Architecture
Kafka Streams requires no separate processing cluster and uses Kafka as its internal messaging layer.Read 30 Sep 2026 · kafka.apache.org
Commercial support
The Apache Software Foundation says it does not sell its software or provide formal or commercial support for its packages.Read 30 Sep 2026 · apache.org
Processing
Kafka Streams processes and analyzes data stored in Kafka, including event-time processing, windowing, and real-time application-state queries.Read 30 Sep 2026 · kafka.apache.org
Processing semantics
Kafka Streams supports exactly-once processing semantics.Read 30 Sep 2026 · kafka.apache.org
Programming
Kafka Streams supports standard Java and Scala applications.Read 30 Sep 2026 · kafka.apache.org
Scalability
Applications can run on one machine for a proof of concept and scale across multiple machines for high-volume production workloads.Read 30 Sep 2026 · kafka.apache.org
Security reporting
Apache asks potential security vulnerabilities to be reported first to private security mailing lists.Read 30 Sep 2026 · apache.org
State
Kafka Streams supports fault-tolerant local state for stateful operations such as windowed joins and aggregations.Read 30 Sep 2026 · kafka.apache.org

Plans and prices

Apache Kafka Streams Free available for download by anyone · no formal or commercial support Read 30 Sep 2026 · apache.org

Every Kafka Streams plan and price →

Strong points and limits

Strong points

  • Supports event-time processing and windowing.
  • Offers exactly-once processing semantics.
  • Runs without a separate processing cluster.
  • Supports fault-tolerant local state.
  • Deploys to containers, VMs, bare metal, or cloud.

Limits

  • Supports Java and Scala only.
  • No formal or commercial support from the foundation.
  • Requires Kafka clusters for input and output data.

Who it suits

Kafka Streams suits developers building Java or Scala applications and microservices that process Kafka data. It can serve a single-machine proof of concept or scale across multiple machines for production workloads.

Verdict

Kafka Streams provides stateful stream-processing APIs that use Kafka as their messaging layer. It is free under Apache License 2.0, but formal or commercial support is not provided by the Apache Software Foundation.

Where Specifiction places it

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