Kafka Streams in Action, Second Edition

13 Kafka Streams Interactive Queries

This chapter covers

• Learning about querying the state of a Kafka Streams application
• Discovering what’s required to enable Interactive Queries
• Building an Interactive Queries app with Spring Boot

Earlier in this book, you learned how to build stateful applications in Kafka Streams. When you enable a stateful operation like an aggregation, Kafka Streams creates a state store to hold the calculation results.

The point of running an aggregation or something similar is you need to gain information or insight from the combined values that it contains. For example, your application keeps track of failed login attempts. Too many indicate someone is trying to gain illegal entry into an account or machine. ...