Designing a Read-Heavy, Highly Available Relational Database on AWS
A company is deploying a web application on AWS that requires a relational database. The application is read-heavy and expects sudden spikes in traffic. The database must be highly available and perform well under load. Which database configuration meets these requirements?
Quick Answer
The correct answer is to deploy Amazon RDS in a Multi-AZ configuration and use read replicas to offload read traffic. This combination directly addresses the need for a read-heavy relational database with high availability: Multi-AZ synchronously replicates data to a standby instance in a different Availability Zone, ensuring automatic failover during an outage, while read replicas handle sudden spikes in read traffic by distributing queries across multiple, asynchronously updated copies. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your ability to distinguish between availability and scalability—a common trap is choosing Multi-AZ alone, which provides high availability but does nothing for read performance under load. Remember the memory tip: “Multi-AZ for the fail, read replicas for the trail”—one keeps you up, the other keeps you fast.
⚠ Common exam trap
Test-takers frequently confuse Multi-AZ with read replicas, assuming Multi-AZ alone provides read scaling, but Multi-AZ only provides failover redundancy—the standby instance cannot serve reads, so read replicas are required to offload read traffic.
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
✓
Deploy Amazon RDS in a Multi-AZ configuration and use read replicas to offload read traffic.
It combines Multi-AZ deployment for high availability with read replicas to offload read traffic, addressing both the read-heavy workload and sudden traffic spikes. Multi-AZ ensures automatic failover to a standby instance in a different Availability Zone if the primary fails, while read replicas distribute read queries across multiple copies, reducing load on the primary database and improving performance under spike conditions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use Amazon ElastiCache for Memcached as the primary database.
Why it's wrong here
ElastiCache for Memcached is an in-memory cache, not a relational engine, so it cannot store the application's relational data or provide durable storage. It tempts because caching offloads read-heavy traffic and absorbs spikes, but it belongs in front of a database, not as the primary datastore.
- ✗
Deploy Amazon RDS in a Multi-AZ configuration without read replicas.
Why it's wrong here
Multi-AZ provides synchronous standby failover for availability, but the standby cannot serve reads, so read-heavy load is not distributed and sudden traffic spikes are not absorbed. It tempts because Multi-AZ satisfies the high-availability requirement, yet read scaling demands read replicas.
- ✗
Deploy Amazon RDS in a single Availability Zone with a large instance size.
Why it's wrong here
A single Availability Zone offers no failover, so an AZ outage takes the database down, failing the high-availability requirement regardless of instance size. It tempts because a large instance handles heavier load, but vertical scaling cannot address read distribution or AZ-level resilience.
- ✓
Deploy Amazon RDS in a Multi-AZ configuration and use read replicas to offload read traffic.
Why this is correct
Multi-AZ provides synchronous standby failover for high availability, while read replicas serve read-heavy traffic on separate instances, absorbing sudden spikes without loading the primary. This satisfies both the availability and read-performance constraints, unlike Multi-AZ alone, which does not offload reads.
Go deeper
Related to this question
About these practice questions
Courseiva writes every SAP-C02 question from scratch — 984 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
4 more ways this is tested on SAP-C02
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 company is deploying a web application on AWS. The application requires a relational database with read replicas for scaling read queries. The database must support automatic failover and be Multi-AZ. Which database solution meets these requirements?
medium- A.Amazon DynamoDB with global tables
- ✓ B.Amazon Aurora with Multi-AZ and Aurora Replicas
- C.Amazon ElastiCache for Redis with replication groups
- D.Amazon RDS for MySQL with Multi-AZ and Read Replicas
Why B: Amazon Aurora with Multi-AZ and Aurora Replicas (Option B) is the correct choice because it provides a single integrated solution where Aurora Replicas serve as both read replicas for scaling read queries and automatic failover targets. In contrast, Amazon RDS for MySQL with Multi-AZ and Read Replicas (Option D) uses a separate Multi-AZ standby for failover and read replicas that are not automatically promoted; while it technically meets the individual requirements, it does not provide the combined failover and read scaling within the same tier, making Aurora the preferred solution. Option A is a NoSQL database, not relational. Option C is a caching service, not a relational database.
Variation 2. A company is designing a new application that requires a relational database. The application has variable traffic, with high spikes during business hours and low traffic at night. The company wants to minimize costs while ensuring the database can handle the spikes. Which solution should the architect recommend?
medium- ✓ A.Use Amazon RDS with Multi-AZ and read replicas, or Amazon Aurora Serverless
- B.Use Amazon RDS with a Single-AZ instance and automatic scaling
- C.Use Amazon DynamoDB with on-demand capacity
- D.Use Amazon RDS with a Single-AZ instance and a large instance size
Why A: Amazon Aurora Serverless automatically scales compute capacity based on application demand, making it ideal for variable traffic with high spikes during business hours and low traffic at night, while minimizing costs by only paying for consumed resources. Multi-AZ RDS with read replicas provides high availability and read scaling but does not automatically scale compute for write spikes, so Aurora Serverless is the more cost-effective and fully managed solution for this use case.
Variation 3. A company is designing a new application that requires a relational database. The application has variable workloads with predictable spikes. The company wants to minimize costs while ensuring that the database can handle the spikes. Which Amazon RDS feature should the company use?
medium- A.RDS Storage Auto Scaling
- B.Read Replicas
- ✓ C.RDS Proxy
- D.Multi-AZ deployment
Why C: RDS Proxy is correct because it pools and shares database connections, allowing the application to handle unpredictable spikes in traffic without provisioning excessive database capacity. It reduces the overhead of opening new connections during peak loads, which is critical for variable workloads with predictable spikes. This connection pooling minimizes the need for over-provisioned RDS instances, directly lowering costs while maintaining performance during spikes.
Variation 4. A company is designing a new application that will be deployed on AWS. The application requires a relational database with automatic failover and high availability within a single AWS region. Which database deployment option meets these requirements?
easy- A.Amazon RDS Single-AZ deployment
- B.Amazon RDS with Read Replicas
- ✓ C.Amazon RDS Multi-AZ deployment
- D.Amazon RDS cross-region replication
Why C: RDS Multi-AZ provides automatic failover and high availability within a region. Option A is wrong because Single-AZ does not provide failover. Option B is wrong because Read Replicas are for read scaling, not failover. Option D is wrong because cross-region replication is for disaster recovery, not primary failover.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 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 SAP-C02 exam.