- A
Amazon Aurora
Why wrong: Relational database, not designed for extremely high write volumes of small records.
- B
Amazon DynamoDB
Handles high write throughput and supports efficient point queries with sort key.
- C
Amazon ElastiCache for Redis
Why wrong: Cache, not durable; data loss risk.
- D
Amazon RDS for MySQL
Why wrong: Relational database not optimized for high-velocity time-series writes.
Question 756 of 1,730
Retrieve Most Recent IoT Reading per Device with DynamoDB Sort Key Pattern
This DBS-C01 practice question tests your understanding of workload-specific database design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is designing a database for an IoT application that receives millions of sensor readings per second. Each reading is a small JSON payload (timestamp, device_id, metric, value). The primary query pattern retrieves the most recent reading for a given device. Which AWS database service is BEST suited for this workload?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"primary"Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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 DynamoDB
Amazon DynamoDB is best suited because it is a fully managed NoSQL key-value database that delivers single-digit millisecond latency at any scale. The primary query pattern—retrieving the most recent reading for a given device—maps directly to a DynamoDB table with a composite primary key (device_id as partition key, timestamp as sort key) and a Query operation with ScanIndexForward=false and Limit=1. This design handles millions of writes per second with consistent performance, unlike relational databases that struggle with such high-velocity ingestion.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Aurora
Why it's wrong here
Relational database, not designed for extremely high write volumes of small records.
- ✓
Amazon DynamoDB
Why this is correct
Handles high write throughput and supports efficient point queries with sort key.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon ElastiCache for Redis
Why it's wrong here
Cache, not durable; data loss risk.
- ✗
Amazon RDS for MySQL
Why it's wrong here
Relational database not optimized for high-velocity time-series writes.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose ElastiCache for Redis because they assume 'most recent reading' implies a caching solution, but the question specifies a database for the workload, and Redis lacks the durability and query flexibility (e.g., filtering by timestamp range) needed for a primary data store of sensor readings.
Detailed technical explanation
How to think about this question
DynamoDB's adaptive capacity automatically partitions hot keys (e.g., a device with frequent updates) across multiple internal partitions, ensuring consistent performance even if a single device_id receives millions of writes. The Query operation with ScanIndexForward=false leverages the LSI or sort key index to retrieve the most recent item in O(log n) time without scanning all items. In a real-world scenario, you would also enable DynamoDB Streams to trigger downstream processing (e.g., anomaly detection) without impacting write throughput.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon DynamoDB — Amazon DynamoDB is best suited because it is a fully managed NoSQL key-value database that delivers single-digit millisecond latency at any scale. The primary query pattern—retrieving the most recent reading for a given device—maps directly to a DynamoDB table with a composite primary key (device_id as partition key, timestamp as sort key) and a Query operation with ScanIndexForward=false and Limit=1. This design handles millions of writes per second with consistent performance, unlike relational databases that struggle with such high-velocity ingestion.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This DBS-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 DBS-C01 exam.
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