SAP-C02 KCL Worker-Shard Mapping Practice Question
A company runs a real-time analytics platform on Amazon Kinesis Data Streams with multiple consumers. The stream is provisioned with 10 shards. One consumer is falling behind, causing data latency. The consumer reads data using the Kinesis Client Library (KCL). Which action will improve the consumer's processing throughput?
⚠ Common exam trap
Candidates often think that increasing shards directly improves consumer throughput, but the consumer's processing capacity depends on the number of workers. Adding shards without adding workers can worsen the lag.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the number of EC2 instances running the consumer application.
The Kinesis Client Library (KCL) distributes shard processing across workers. Increasing the number of EC2 instances running the consumer application adds more workers, allowing parallel processing of shards and thus improving throughput for the lagging consumer. Option A is incorrect because decreasing the batch size reduces the number of records processed per call, which typically lowers throughput. Option B is incorrect because increasing the number of shards increases the stream's total capacity but does not directly help a consumer that is already falling behind; it may actually require more workers to handle the additional shards. Option C is incorrect because extending the retention period affects how long data is stored, not how quickly it is processed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Decrease the batch size in the KCL configuration.
Why it's wrong here
Decreasing the batch size reduces the number of records processed per call, which typically lowers throughput, not improves it.
- ✗
Increase the number of shards in the Kinesis stream.
Why it's wrong here
Increasing the number of shards increases stream capacity but does not directly help a lagging consumer; it may require more workers to handle the extra shards.
- ✗
Increase the Kinesis stream's retention period to 7 days.
Why it's wrong here
Extending the retention period affects data availability, not processing speed.
- ✓
Increase the number of EC2 instances running the consumer application.
Why this is correct
Adding more EC2 instances adds workers, allowing KCL to distribute shards across them, increasing parallel processing and improving throughput.
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