[Solved] You want to create a topology that reads from two topics, merges their streams, filters messages with key starting with 'A', and writes to a single... Which code snippet correctly builds this? | Kafka

Kafka - Streams

You want to create a topology that reads from two topics, merges their streams, filters messages with key starting with 'A', and writes to a single output topic. Which code snippet correctly builds this?

A

KStream<String,String> s1 = builder.stream("topic1");
KStream<String,String> s2 = builder.stream("topic2");
KStream<String,String> merged = s1.merge(s2);
merged.filter((k,v) -> k.startsWith("A")).to("output");

B

KStream<String,String> merged = builder.stream("topic1", "topic2");
merged.filter((k,v) -> v.startsWith("A")).to("output");

C

KStream<String,String> s1 = builder.stream("topic1");
KStream<String,String> s2 = builder.stream("topic2");
s1.filter((k,v) -> k.startsWith("A")).to("output");
s2.to("output");

Dbuilder.stream("topic1").filter((k,v) -> k.startsWith("A")).to("output"); builder.stream("topic2").filter((k,v) -> k.startsWith("A")).to("output");

Step-by-Step Solution

Solution:

Step 1: Identify correct merging of two streams
KStream s1 = builder.stream("topic1"); KStream s2 = builder.stream("topic2"); KStream merged = s1.merge(s2); merged.filter((k,v) -> k.startsWith("A")).to("output"); merges two streams explicitly using merge().
Step 2: Check filtering and output
Filter is applied on merged stream, then sent to one output topic.
Step 3: Exclude incorrect options
KStream merged = builder.stream("topic1", "topic2"); merged.filter((k,v) -> v.startsWith("A")).to("output"); incorrectly filters on value instead of key; C and D write separately, not merged.
Final Answer:
Explicitly merges two streams using merge(), filters keys starting with 'A', and writes to output -> Option A
Quick Check:
Merge streams then filter and output [OK]

Quick Trick: Use merge() to combine streams before filtering [OK]

Common Mistakes:

MISTAKES

Trying to stream multiple topics in one call
Writing streams separately instead of merged
Filtering before merging incorrectly

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Which code snippet correctly builds this?

Step 1: Identify correct merging of two streams

Step 2: Check filtering and output

Step 3: Exclude incorrect options

Final Answer:

Quick Check:

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