What is kappa architecture?

Kappa architecture is an alternative big data architectural pattern to lambda architecture. It aims to simplify big data pipelines by using a single stream processing system to handle both real-time and historical analytics.

Kappa avoids the complexity of maintaining separate batch and streaming ecosystems as required in lambda architecture. It relies entirely on fast, scalable stream processing engines and storage optimized for streams access patterns.

With stream processors becoming more powerful and faster storage like Kafka, the benefits of separate batch processing have diminished in many use cases. Kappa leverages unified processing on streams to reduce complexity of deploying and maintaining hybrid systems.

For example, a kappa pipeline would implement both real-time alerts and aggregated historical reports using just stream processing. The raw stream is stored efficiently for reprocessing. No separate batch jobs or storage are needed.

Kappa reduces the overhead of reconciling between dual pipelines in lambda. But lambda allows reprocessing historical data independently from real-time streams. The optimal choice depends on access patterns, data volumes and system constraints.

What does it do? How does it work?

In kappa architecture, all data flows through a single stream processing pipeline. Queries are handled by the same stream processing system used to ingest and process both real-time and historical data.

Data is queried directly from streams by partitioning streams and data replaying for historical queries. No separate batch system or coordination is required.

Why is it important? Where is it used?

Kappa architecture gained popularity as a lower complexity alternative to lambda architectures for big data workloads. It leverages stream processing improvements and storage optimizations to handle both real-time and historical processing.

Modern streaming platforms make kappa a viable option. Use cases include web analytics, metrics monitoring, IoT, fraud detection and any workload requiring unified stream processing.

FAQ

How does kappa architecture differ from lambda architecture?

Kappa only uses stream processing while lambda combines stream and batch processing. Kappa queries rely on streams rather than pre-computed stores.

What are the main benefits of kappa architecture?

Benefits include simplified stream processing, no duplication of business logic between streams and batches, no coordination overhead and easier operational management.

What are the downsides of kappa architecture?

Downsides include potentially slower historical queries, complications of exactly-once semantics, and generally less maturity than robust batch systems optimized for cost and throughput.

When is kappa architecture a good choice?

Kappa excels for workloads where:

• Low latency reads and updates are critical
• No need for complex, long-running batch jobs
• Stream processing can cost-effectively scale to manage data volumes

References:

• [Book] Deciphering Data Architectures by O'Reilly Media, Inc.
• [Post] What every software engineer should know about real-time data's unifying abstraction
• [Post] General-purpose Stream Joins via Pruning Symmetric Hash Joins
• [Post] Lambda and Kappa Architectures in Brief
• [Post] Kappa Architecture is Mainstream Replacing Lambda