- A
Amazon RDS for PostgreSQL with an index on score
Why wrong: RDS has higher latency and less suitable for real-time.
- B
Amazon DynamoDB with a global secondary index on score
Why wrong: DynamoDB can't natively maintain a sorted set with sub-millisecond updates.
- C
Amazon ElastiCache for Redis with a sorted set
Redis sorted sets provide O(log N) operations and sub-millisecond latency.
- D
Amazon Neptune with a graph model
Why wrong: Neptune is for graph data, not leaderboards.
Question 538 of 1,786
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. 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 data engineer is designing a data store for a real-time leaderboard application that requires sub-millisecond read and write latency. The leaderboard stores scores for millions of users and needs to be sorted by score. Which AWS service should the engineer use?
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 ElastiCache for Redis with a sorted set
Amazon ElastiCache for Redis provides a sorted set data structure (ZADD/ZRANGE commands) that maintains elements ordered by a numeric score with O(log N) complexity for both writes and reads, enabling sub-millisecond latency for real-time leaderboard updates and queries. This is the only option purpose-built for in-memory, sorted, real-time leaderboards at scale.
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 RDS for PostgreSQL with an index on score
Why it's wrong here
RDS has higher latency and less suitable for real-time.
- ✗
Amazon DynamoDB with a global secondary index on score
Why it's wrong here
DynamoDB can't natively maintain a sorted set with sub-millisecond updates.
- ✓
Amazon ElastiCache for Redis with a sorted set
Why this is correct
Redis sorted sets provide O(log N) operations and sub-millisecond latency.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon Neptune with a graph model
Why it's wrong here
Neptune is for graph data, not leaderboards.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose DynamoDB (Option B) because it is a common NoSQL choice for high-performance applications, but they overlook that DynamoDB lacks a native sorted data structure and requires costly scan operations to retrieve a globally sorted leaderboard, whereas Redis sorted sets are purpose-built for this exact use case.
Detailed technical explanation
How to think about this question
Redis sorted sets use a skip list and hash table internally, allowing O(log N) for add/update operations and O(log N + M) for range queries like top N scores. The ZREVRANGE command retrieves the highest scores in reverse order, and ZADD updates scores atomically, making it ideal for leaderboards that change frequently. In practice, a single Redis node can handle hundreds of thousands of operations per second, but for millions of users, clustering (Redis Cluster) may be needed to shard data while preserving sorted set semantics within each shard.
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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Data Store Management — study guide chapter
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon ElastiCache for Redis with a sorted set — Amazon ElastiCache for Redis provides a sorted set data structure (ZADD/ZRANGE commands) that maintains elements ordered by a numeric score with O(log N) complexity for both writes and reads, enabling sub-millisecond latency for real-time leaderboard updates and queries. This is the only option purpose-built for in-memory, sorted, real-time leaderboards at scale.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 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.
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