DBS-C01 Workload-Specific Database Design Practice Question
A startup is building a mobile application that requires a database to store user preferences and session data. The data is accessed by user ID and requires single-digit millisecond latency. The workload is read-heavy with occasional writes. Which database service is MOST cost-effective?
⚠ Common exam trap
It's easy for candidates to choose Amazon ElastiCache for Memcached (Option B) because of its low latency, but they overlook the requirement for a durable database that persists session data, whereas Memcached is a volatile cache with no built-in persistence or replication for data durability.
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 with on-demand capacity
Amazon DynamoDB with on-demand capacity is the most cost-effective choice because it provides single-digit millisecond latency for key-value lookups by user ID, scales automatically to handle read-heavy workloads with occasional writes, and charges only for the reads and writes consumed, avoiding the cost of provisioning for peak capacity. The on-demand mode eliminates the need for capacity planning, making it ideal for unpredictable or variable traffic patterns typical of a startup's mobile application.
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 Serverless
Why it's wrong here
Aurora Serverless is relational and more expensive for simple key-value access.
- ✗
Amazon ElastiCache for Memcached
Why it's wrong here
ElastiCache is a cache, not a durable database; data loss risk.
- ✓
Amazon DynamoDB with on-demand capacity
Why this is correct
DynamoDB provides single-digit millisecond latency and is cost-effective for variable read-heavy workloads.
- ✗
Amazon RDS for MySQL with provisioned IOPS
Why it's wrong here
RDS is relational and may be more expensive for simple key-value access.
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Same concept, more angles
2 more ways this is tested on DBS-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 startup is building a mobile application that needs to store user profiles and preferences. The data is schema-less and will grow rapidly. The application requires single-digit millisecond latency for reads and writes. Which AWS database should they choose?
easy- A.Amazon Aurora (MySQL compatible)
- B.Amazon Redshift
- C.Amazon RDS for SQL Server
- ✓ D.Amazon DynamoDB
Why D: Amazon DynamoDB is a fully managed NoSQL key-value and document database that delivers single-digit millisecond latency at any scale. It is schema-less, making it ideal for storing user profiles and preferences that have varying attributes, and it automatically scales to handle rapid growth without downtime or performance degradation.
Variation 2. A startup is building a social media application. User profiles, posts, and comments have relationships but the team expects rapid growth and wants to scale horizontally with no single points of failure. They need a database that supports flexible schemas for different content types. Which database service is most appropriate?
easy- ✓ A.Amazon DynamoDB
- B.Amazon Neptune
- C.Amazon Redshift
- D.Amazon RDS for MySQL
Why A: Amazon DynamoDB is the most appropriate choice because it is a fully managed NoSQL key-value and document database that supports flexible schemas, enabling the application to handle user profiles, posts, and comments with varying attributes. It scales horizontally by automatically partitioning data across multiple nodes, and its multi-AZ replication eliminates single points of failure, meeting the startup's requirements for rapid growth and high availability.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.