KStream and KTable concepts in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a KStream in Kafka Streams?

A KStream is a continuous flow of records where each record represents a single event or update. It models data as an unbounded, real-time stream of events.

beginner

What is a KTable in Kafka Streams?

A KTable is a changelog stream that represents a table of key-value pairs. It models data as a snapshot of the latest state for each key, updating over time.

intermediate

How does a KStream differ from a KTable?

A KStream represents each event as a separate record (event-driven), while a KTable represents the latest value for each key (state-driven). KStream is like a log of changes; KTable is like a database table with current state.

beginner

What happens when you update a key in a KTable?

The KTable updates the value for that key, replacing the old value with the new one. This means the table always holds the latest state for each key.

intermediate

Can you perform joins between KStreams and KTables?

Yes, Kafka Streams supports joins between KStreams and KTables. For example, joining a KStream with a KTable enriches the stream events with the latest state from the table.

Which Kafka Streams abstraction represents a continuous stream of events?

A KTable

B KConsumer

C KTopic

D KStream

KStream models a continuous flow of event records in Kafka Streams.

What does a KTable represent?

A A Kafka topic partition

B A stream of individual events

C A snapshot of the latest state per key

D A consumer group

KTable represents the latest value for each key, like a table of current state.

If you want to keep track of the latest user profile info, which abstraction should you use?

A KTable

B Kafka Producer

C KStream

D Kafka Topic

KTable holds the latest state per key, ideal for user profiles.

What happens when a key is updated in a KTable?

A The old value is replaced with the new value

B A new event is appended without changing old data

C The key is deleted

D The update is ignored

KTable updates the value for the key to keep the latest state.

Which join enriches a stream of events with the latest state from a table?

A KStream-KStream join

B KStream-KTable join

C Kafka topic join

D KTable-KTable join

Joining a KStream with a KTable adds the latest table state to each stream event.

Explain in your own words the difference between a KStream and a KTable.

Think about a log of events versus a database table.

Describe a real-life example where you would use a KTable instead of a KStream.

Consider situations where you want to know the current status, not every change.