Apache Kafka

Free plan APISelf-hosted

What Apache Kafka is

Apache Kafka is open-source, self-hosted software for stream processing. It supports stateful processing and event-time windows, and its listed delivery guarantee is both. Teams can run Kafka themselves and use Java or Scala as supported languages. Its client language options are broader: Java, Scala, Go, Python, C, C++, and REST APIs are listed.

Kafka has a free pricing model and a free plan. SQL processing is not supported. The project’s listed founding year is 1999, and its website is kafka.apache.org. These characteristics make Kafka relevant to teams choosing a stream-processing system that they can self-host, especially when stateful processing, event-time windows, delivery guarantees, and client language options matter. The supported-language list and client-language list describe different scopes: Java and Scala are named as supported languages, while the client options also include Go, Python, C, C++, and REST APIs. Buyers can weigh those capabilities against the absence of SQL processing when deciding whether Kafka fits their stream-processing needs.

Who it suits

Kafka suits teams looking for free, open-source stream-processing software they can self-host. It is relevant when stateful processing, event-time windows, delivery guarantees, and its supported languages or client options fit a team’s requirements.

What it does well

Free and open source.
Self-hosted deployment model.
Supports stateful processing and event-time windows.
Delivery guarantee is listed as both.
Client options include Java, Scala, Go, Python, C, C++, and REST APIs.

What to know first

SQL processing is not supported.
Teams must use the self-hosted deployment model.

Plans

Plan	Billed and limits	Price
Apache Kafka	Available to download for free · No formal or commercial support from ASF	Free

As kafka.apache.org lists them, read 9 Oct 2026. The maker's own page has the final word.

Getting started

Visit kafka.apache.org.
Plan to deploy Kafka as self-hosted software.
Choose Java or Scala from its supported languages, or select from its listed client options.

Verdict

Choose Apache Kafka if you need a free, open-source stream-processing system that supports stateful processing and event-time windows and can be self-hosted. Its listed client options cover several languages and REST APIs. Look elsewhere if SQL processing is required.

Questions

How much does Apache Kafka cost?

Kafka has a free pricing model and a free plan; it is open source.

Can Kafka be self-hosted?

Yes. Its deployment model is self-hosted.

Does Kafka support SQL processing?

No. SQL processing is listed as unsupported.

Which languages does Kafka support?

Java and Scala are listed as supported languages. Client options also include Go, Python, C, C++, and REST APIs.

Does Kafka support stateful processing and event-time windows?

Yes. Both are listed as supported capabilities.

What is Kafka’s delivery guarantee?

Its delivery guarantee is listed as both.

Facts from Apache Kafka's own pages

Availability and durability: Kafka supports durable, fault-tolerant storage and replication across availability zones, data centers, or geographic regions. · kafka.apache.org, 9 Oct 2026
Deployment: Kafka can run on bare-metal hardware, virtual machines, or containers, on premises or in the cloud, with self-managed or vendor-managed service options. · kafka.apache.org, 9 Oct 2026
Event streaming: Kafka lets applications publish and subscribe to event streams, store them durably, and process them in real time or retrospectively. · kafka.apache.org, 9 Oct 2026
Founded: 1999 · kafka.apache.org, 4 Oct 2026
Integrations: Kafka Connect integrates with hundreds of event sources and sinks; the homepage names Postgres, JMS, Elasticsearch, and AWS S3 as examples. · kafka.apache.org, 9 Oct 2026
License: The Apache Software Foundation identifies Apache License 2.0 as a widely adopted open-source license. · apache.org, 9 Oct 2026
Performance and scale: The project describes throughput at network-limited rates, latencies as low as 2 ms, and scaling to clusters of up to a thousand brokers. · kafka.apache.org, 9 Oct 2026
Quickstart requirement: The Kafka quickstart says a local environment must have Java 17 or later installed. · kafka.apache.org, 9 Oct 2026
Security: The project describes Kafka as secure; the ASF directs vulnerability reports to its security page. · kafka.apache.org, 9 Oct 2026
Stream processing: Kafka Streams supports stateful operations, aggregations, windowing, joins, event-time processing, and exactly-once processing. · kafka.apache.org, 9 Oct 2026
Support: The Apache Software Foundation says it does not provide formal or commercial support for its software packages. · apache.org, 9 Oct 2026
Use cases: The project lists messaging, website activity tracking, metrics, log aggregation, stream processing, event sourcing, and commit logs as Kafka use cases. · kafka.apache.org, 9 Oct 2026
What it does: Apache Kafka is an open-source distributed event streaming platform for data pipelines, streaming analytics, data integration, and mission-critical applications. · kafka.apache.org, 9 Oct 2026