DEA-C01 Data Ingestion and Transformation Practice Question
A company is using Amazon Kinesis Data Firehose to ingest clickstream data from a website into an S3 bucket. The data is then analyzed using Amazon Athena. Recently, the company noticed that Athena queries are returning incomplete results for the last 30 minutes of data. The Firehose delivery stream is configured to buffer data for 60 seconds or 5 MB before delivering to S3. The S3 bucket has a lifecycle policy that transitions objects to Amazon S3 Glacier after 30 days. The IAM role for Firehose has permissions to write to S3 and access a CloudWatch Logs group. The engineer checks the Firehose monitoring and sees that the delivery rate is healthy, but the 'S3.Bytes' metric shows a spike in the last hour. The 'BackupToS3.Bytes' metric is zero. What is the MOST likely cause of the missing data?
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
✓
The data is still being buffered in Firehose and has not yet been delivered to S3.
The data is still being buffered in Firehose and has not yet been delivered to S3. The buffer settings (60 seconds or 5 MB) mean data can be held in the buffer for up to 60 seconds before being written to S3. For the last 30 minutes, some data may still be in the buffer and not yet delivered. Athena queries only see data that has been delivered to S3. Option A (lifecycle policy) would not affect recent data. Option B (backup) is unrelated and the 'BackupToS3.Bytes' metric is zero, indicating backup is not active. Option D (IAM permissions) would cause errors, not missing data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The lifecycle policy is transitioning data before Athena can query it.
Why it's wrong here
The lifecycle policy transitions data to S3 Glacier after 30 days, but the issue is with recent 30 minutes of data. Athena queries are not affected by lifecycle policies on such short timeframes.
- ✗
The backup is enabled and data is being sent to the backup bucket instead.
Why it's wrong here
Backup is not enabled, as indicated by the 'BackupToS3.Bytes' metric being zero. Therefore, data is not being sent to a backup bucket.
- ✓
The data is still being buffered in Firehose and has not yet been delivered to S3.
Why this is correct
The data is still being buffered in Firehose. With buffer settings of 60 seconds or 5 MB, data can be held for up to 60 seconds before delivery. Athena queries only see data that has been delivered to S3, so data still in the buffer is missing from query results.
- ✗
The IAM role for Firehose does not have permissions to write to the S3 bucket.
Why it's wrong here
The IAM role for Firehose has permissions to write to S3, as indicated by the healthy delivery rate and the 'S3.Bytes' metric showing activity. If there were permission issues, errors would appear in CloudWatch Logs and delivery would fail.
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 |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.