DEA-C01 Data Store Management Practice Question
A data engineer needs to store and analyze time-series data from IoT devices. The data volume is 10 GB per day, and the queries are mostly on the most recent 7 days of data. The engineer wants to minimize storage costs while retaining historical data for 1 year. Which combination of AWS services is most cost-effective?
⚠ Common exam trap
A common mix-up: candidates choose DynamoDB with TTL and S3 for archival (Option B) because it seems cost-effective, but they overlook the operational complexity and query latency of accessing historical data in S3, which violates the 'minimize storage costs while retaining historical data for 1 year' requirement without considering query patterns.
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
✓
Amazon Timestream
Amazon Timestream is purpose-built for time-series data, offering automatic tiering between in-memory (for recent 7 days) and magnetic stores (for historical data up to 1 year). This matches the query pattern (mostly recent 7 days) and retention requirement (1 year) while minimizing storage costs through its serverless, pay-per-query model. Timestream also supports time-series-specific functions like interpolation and smoothing, making it more efficient than general-purpose databases for this workload.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Amazon Timestream
Why this is correct
Timestream is cost-effective for time-series data with automatic storage tiering.
- ✗
Amazon DynamoDB with TTL and S3 for archival
Why it's wrong here
DynamoDB's cost model for high-volume writes (10 GB/day) makes it prohibitively expensive for ingesting and storing this scale of time-series data compared to purpose-built solutions, especially for analytical queries over a 7-day range. However, DynamoDB with TTL is a tempting choice for its automatic data expiry, making it suitable for operational data requiring low-latency access to individual items and simple range queries, with S3 providing cost-effective long-term archival.
- ✗
Amazon Redshift
Why it's wrong here
Redshift is more expensive and designed for analytic queries, not time-series specifically.
- ✗
Amazon RDS with MySQL
Why it's wrong here
RDS is not optimized for time-series data and can be costly for high-volume writes.
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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Same concept, more angles
1 more way this is tested on DEA-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A data engineer is designing a data store for a time-series application that requires sub-millisecond read latency for the latest data and high ingestion rates. Which AWS service is most suitable?
medium- A.Amazon DynamoDB
- B.Amazon ElastiCache for Redis
- C.Amazon RDS for PostgreSQL
- ✓ D.Amazon Timestream
Why D: Amazon Timestream is purpose-built for time-series data, offering sub-millisecond read latency for recent data via its in-memory store and supporting high ingestion rates with automatic partitioning and tiering. It is the most suitable choice because it natively handles time-series workloads without requiring manual tuning or schema optimization.
JA
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.