Check out the docs at Apache Kafka web site: http://kafka.apache.org/documentation/streams/

Sub-pages:

• Using Kafka Streams:
  
  • Usage Patterns
  • Application Reset Tool

  • Join Semantics

  • Streams FAQs
  • Data (Re)Processing Scenarios
• Development:
  • KIP overview by release
  • Development Plan
  • Discussions
  • Data (Re)Processing Scenarios
  • Kafka Streams DSL Grammar
• Internals:
  
  • Data Management
  • Architecture
  • DSL Optimizer

Find more links about Kafka Streams at Kafka Ecosystem page.

Kafka Streams related KIPs:

Below is a list of KIPs that are not release yet. Go to Kafka Streams KIP Overview for KIPs by release (including discarded KIPs).

Under discussion

• KIP-228 Negative record timestamp support
• KIP-424: Allow suppression of intermediate events based on wall clock time
• KIP-439: Cleanup built-in Store interfaces
• KIP-448: Add State Stores Unit Test Support to Kafka Streams Test Utils
• KIP-508: Make Suppression State Queriable
• KIP-513: Distinguish between Key and Value serdes in scala wrapper library for kafka streams
• KIP-540: Implement per key stream time tracking
• KIP-560: Auto infer external topic partitions in stream reset tool
• KIP-571: Add option to force remove members in StreamsResetter
• KIP-572: Improve timeouts and retries in Kafka Streams
• KIP-591: Add Kafka Streams config to set default store type
• KIP-598: Augment TopologyDescription with store and source / sink serde information

Adopted

• inactive (feel free to pick up):
  • KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner (partially implemented in v1.1)
  • KIP-258: Allow to Store Record Timestamps in RocksDB (partially implemented in v2.3)
  • KIP-300: Add Windowed KTable API in StreamsBuilder (accepted but postponed because current code base does not allow to implement it as proposed) 
  • KIP-328: Ability to suppress updates for KTables (partially implemented in v2.1)
  • KIP-471: Expose RocksDB Metrics in Kafka Streams (partially implemented in v2.4; completion deferred to next major release)
• WIP:
  • KIP-216: IQ should throw different exceptions for different errors
  • KIP-399: Extend ProductionExceptionHandler to cover serialization exceptions
  • KIP-401: TransformerSupplier/ProcessorSupplier StateStore connecting
  • KIP-441: Smooth Scaling Out for Kafka Streams
  • KIP-444: Augment metrics for Kafka Streams (partially implemented in v2.4 and v2.5)
  • KIP-447: Producer scalability for exactly once semantics
  • KIP-466: Add support for List<T> serialization and deserialization
  • KIP-478 - Strongly typed Processor API
  • KIP-557: Add emit on change support for Kafka Streams
• upcoming release Kafka 2.6:
  • KIP-221: Enhance DSL with Connecting Topic Creation and Repartition Hint
  • KIP-446: Add changelog topic configuration to KTable suppress
  • KIP-594: Expose output topic names from TopologyTestDriver

Inactive (feel free to pick up):

• KIP-95: Incremental Batch Processing for Kafka Streams
• KIP-159: Introducing Rich functions to Streams
• KIP-260: add primary join operation for Stream-Stream join (WIP) (draft)
• KIP-311: Async processing with dynamic scheduling in Kafka Streams
• KIP-314: KTable to GlobalKTable Bi-directional Join
• KIP-326: Schedulable KTable as Graph source
• KIP-335: Consider configurations for KafkaStreams
• KIP-362: Support dynamic gap session window
• KIP-378: Enable Dependency Injection for Kafka Streams handlers
• KIP-406: GlobalStreamThread should honor custom reset policy
• KIP-408: Add Asynchronous Processing To Kafka Streams
• KIP-418: A method-chaining way to branch KStream
• KIP-450: Sliding Window Aggregations in the DSL
• KIP-457: Add DISCONNECTED status to Kafka Streams
• KIP-459: Improve KafkaStreams#close
• KIP-463: Auto-configure non-default Serdes passed alongside the TopologyBuilder
• KIP-XXX: [Streams] Support multiple topic resolution in TopicNameExtractor (draft)