Join operations (KStream-KStream, KStream-KTable) in Kafka - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to join two KStreams by key using an inner join.

Kafka

KStream<String, String> joinedStream = stream1.[1](stream2, (value1, value2) -> value1 + value2, JoinWindows.of(Duration.ofMinutes(5)), Joined.with(Serdes.String(), Serdes.String(), Serdes.String()));

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Afilter

BleftJoin

Cjoin

DouterJoin

Attempts:

3 left

💡 Hint

Common Mistakes

Using leftJoin instead of join causes a different join behavior.

Using filter does not perform a join.

The join method performs an inner join between two KStreams based on their keys.

2fill in blank

medium

Complete the code to join a KStream with a KTable using a left join.

Kafka

KStream<String, String> joinedStream = stream.[1](table, (streamValue, tableValue) -> streamValue + (tableValue == null ? "" : tableValue));

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Ajoin

Bfilter

CouterJoin

DleftJoin

Attempts:

3 left

💡 Hint

Common Mistakes

Using join instead of leftJoin excludes stream records without matching table keys.

Using outerJoin is not supported between KStream and KTable.

The leftJoin method joins a KStream with a KTable, including all records from the stream even if the table has no matching key.

3fill in blank

hard

Fix the error in the join window definition for a KStream-KStream join.

Kafka

KStream<String, String> joinedStream = stream1.join(stream2, (v1, v2) -> v1 + v2, JoinWindows.[1](Duration.ofMinutes(10)), Joined.with(Serdes.String(), Serdes.String(), Serdes.String()));

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Aof

BofTimeDifferenceWithNoGrace

CwithTimeDifferenceAndGrace

DofMillis

Attempts:

3 left

💡 Hint

Common Mistakes

Using deprecated or incorrect window methods causes runtime errors.

Using ofMillis expects a long, not a Duration.

The JoinWindows.of(Duration) method defines the join window duration correctly for KStream-KStream joins.

4fill in blank

hard

Fill both blanks to create a KStream-KTable join with correct Serdes and join type.

Kafka

KStream<String, String> result = stream.[1](table, (sValue, tValue) -> sValue + tValue, Joined.with(Serdes.[2], Serdes.String(), Serdes.String()));

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AleftJoin

Bjoin

CString

DInteger

Attempts:

3 left

💡 Hint

Common Mistakes

Using join instead of leftJoin excludes stream records without matching keys.

Using Integer serde for string keys causes serialization errors.

The leftJoin method is used for KStream-KTable joins including all stream records. The key serde is Serdes.String() for string keys.

5fill in blank

hard

Fill all three blanks to create a KStream-KStream join with a 5-minute window and correct join type and serde.

Kafka

KStream<String, String> joined = stream1.[1](stream2, (v1, v2) -> v1 + v2, JoinWindows.[2](Duration.ofMinutes(5)), Joined.with(Serdes.[3], Serdes.String(), Serdes.String()));

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Ajoin

BleftJoin

Cof

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using leftJoin instead of join changes join semantics.

Using incorrect window method causes errors.

Using wrong serde causes serialization issues.

Use join for KStream-KStream inner join, JoinWindows.of(Duration) to set the window, and Serdes.String() for string keys.