DEA-C01 Data Operations and Support Practice Question
A data engineer is using Amazon Kinesis Data Firehose to deliver streaming data to an Amazon S3 bucket. The engineer notices that some data records are missing from S3, and the Firehose delivery stream metrics show increased DeliveryToS3.DataFreshness. The engineer needs to ensure all records are delivered. Which action should the engineer take?
⚠ Common exam trap
The trap here is assuming that increasing buffering or adding shards will fix missing data, but the real issue is delivery errors that require logging to diagnose.
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
✓
Enable error logging on the Firehose delivery stream and review the error output in Amazon CloudWatch Logs.
Enabling error logging on the Firehose delivery stream is crucial for diagnosing why records are not delivered to S3. The logs in CloudWatch will show specific errors such as access denied or invalid records, allowing the engineer to take corrective action. This directly addresses the missing data and high data freshness.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the number of shards in the source Kinesis data stream to improve throughput.
Why it's wrong here
Increasing shards in the source Kinesis data stream can improve ingestion throughput, but Firehose reads from the stream at its own pace. The missing records are likely due to delivery failures to S3, not insufficient source throughput. Adding shards does not address the Firehose delivery errors and may incur additional costs without resolving the issue.
- ✗
Enable Amazon S3 server access logging on the destination bucket to capture failed deliveries.
Why it's wrong here
S3 server access logging records requests made to the bucket, but it does not provide details about why Firehose failed to deliver records. It can help audit access but does not directly resolve missing data or reduce data freshness. The engineer needs to address the root cause of delivery failures, which is likely related to Firehose configuration or permissions, not S3 logging.
- ✓
Enable error logging on the Firehose delivery stream and review the error output in Amazon CloudWatch Logs.
Why this is correct
Enabling error logging for Firehose sends delivery errors to CloudWatch Logs, providing visibility into why records are not delivered. Common causes include insufficient S3 permissions, KMS key issues, or malformed records. Reviewing these logs allows the engineer to identify and fix the root cause, ensuring all records are delivered and reducing data freshness.
- ✗
Configure the Firehose delivery stream to use a longer buffering interval to reduce the number of S3 PUT requests.
Why it's wrong here
Increasing the buffering interval (e.g., from 60 to 900 seconds) allows more data to accumulate before delivery, reducing the frequency of S3 PUTs. However, this increases DataFreshness, meaning data arrives in S3 less frequently, and does not address missing records. The issue is likely due to errors in delivery, not the buffering interval, so this change could worsen the freshness metric.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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