SAP-C02 Design for New Solutions Practice Question
A company is designing a new database solution for a global e-commerce application. The database must support high read and write throughput with single-digit millisecond latency. The company expects traffic spikes during peak hours. Which TWO AWS services should the company consider?
⚠ Common exam trap
It's easy for candidates to choose Amazon Aurora or RDS for MySQL because they are familiar with SQL databases, but they overlook the requirement for single-digit millisecond latency and high throughput under spikes, which in-memory caching and NoSQL solutions like ElastiCache and DynamoDB are specifically designed to meet.
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
Amazon DynamoDB (C) is correct because it is a fully managed NoSQL key-value and document database designed for single-digit millisecond latency at any scale, and it handles high read/write throughput with automatic scaling to absorb peak-hour traffic spikes. Amazon ElastiCache (B) is correct because it provides in-memory caching with sub-millisecond latency using Redis or Memcached, offloading read traffic from the primary database and smoothing bursts during peak hours. Together they fit a global e-commerce workload needing fast, elastic throughput. Amazon DocumentDB (A) is a MongoDB-compatible document database that does not deliver the same single-digit millisecond latency guarantees at scale for this use case. Amazon Aurora (D) and Amazon RDS for MySQL (E) are relational databases that can be fast but are not purpose-built for the extreme, spiky throughput and in-memory caching needs described here.
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 DocumentDB (with MongoDB compatibility)
Why it's wrong here
DocumentDB is a document database whose primary instance handles writes, so it cannot deliver the sustained high write throughput and single-digit millisecond latency at global e-commerce scale. It is tempting because it offers MongoDB compatibility and replica reads, which suit content or catalogue workloads rather than high-throughput transactional ones.
- ✓
Amazon ElastiCache
Why this is correct
ElastiCache provides an in-memory caching layer delivering sub-millisecond read latency, absorbing the read-heavy load and peak-hour spikes so the primary database is not overwhelmed. It satisfies the single-digit millisecond latency and burst throughput constraints, though it is not a durable write store.
- ✓
Amazon DynamoDB
Why this is correct
DynamoDB is a fully managed NoSQL store delivering consistent single-digit millisecond latency at any scale, with on-demand capacity automatically absorbing peak-hour traffic spikes. This satisfies both the high read/write throughput and latency requirements without provisioning or operational overhead.
- ✗
Amazon Aurora
Why it's wrong here
Aurora is a relational engine, so a single writer instance caps write throughput and cannot scale writes horizontally for global spikes. It is tempting because Aurora delivers single-digit millisecond latency and read scaling via replicas, and it would be correct for a relational workload needing high availability rather than massive write scale.
- ✗
Amazon RDS for MySQL
Why it's wrong here
RDS for MySQL runs on a single primary instance, so write throughput cannot scale horizontally and vertical scaling causes downtime during spikes. It is tempting because RDS offers managed MySQL with low latency, and it would be correct for a smaller, predictable relational workload that does not need global scale.
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