SOA-C02 Multi-AZ deployment Practice Question
A company runs a critical database on an RDS for PostgreSQL instance in a single Availability Zone. The database experiences high write latency. The SysOps Administrator needs to improve the database's reliability and performance without downtime. Which solution meets these requirements?
⚠ Common exam trap
Test-takers frequently confuse Multi-AZ (synchronous replication for high availability) with read replicas (asynchronous replication for read scaling), assuming a read replica can improve write performance or reliability when it only helps with 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
✓
Modify the RDS instance to be Multi-AZ with a standby in another Availability Zone.
Enabling Multi-AZ for an RDS for PostgreSQL instance provisions a standby replica in a different Availability Zone and synchronously replicates data to it. This eliminates the single point of failure, improving reliability. The modification is performed as a zero-downtime operation via a DNS update, meeting the requirement for no downtime. Note that Multi-AZ improves availability but does not reduce write latency; performance improvement may come from offloading backups and other administrative tasks to the standby.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Modify the RDS instance to be Multi-AZ with a standby in another Availability Zone.
Why this is correct
Modifying the RDS instance to a Multi-AZ deployment provisions a synchronous standby replica in a different Availability Zone, and Amazon RDS automatically fails over to that standby if an AZ outage or primary instance failure occurs. This change can typically be applied without downtime, as it only requires a metadata modification and provisioning of the standby. This gives the database the high availability and automatic failover that the company needs.
- ✗
Create a Multi-AZ deployment in the same Availability Zone.
Why it's wrong here
A Multi-AZ deployment by definition requires a primary instance and a standby in a separate Availability Zone; if both are in the same AZ, the deployment cannot protect against an AZ-level outage, and RDS does not actually support a same-AZ Multi-AZ configuration. To get the intended failover benefit, the standby must reside in a different AZ, so this option would not meet the requirement even if it were allowed.
- ✗
Increase the allocated storage for the RDS instance.
Why it's wrong here
Increasing allocated storage on an RDS instance raises the storage size and may increase the baseline I/O performance, especially with gp2/gp3 volumes, but this action does nothing to add redundancy, automatic failover, or protection from an Availability Zone failure. The instance remains a single point of failure, so this option does not satisfy the requirement for higher availability.
- ✗
Create a read replica in another Availability Zone and redirect read traffic.
Why it's wrong here
A read replica in another AZ uses asynchronous replication and is designed to offload read traffic, not to provide high availability; if the primary fails, you would have to manually call the promote operation and update application connections, with potential data loss from replication lag. Redirecting read traffic to the replica does not make writes more durable nor provide automatic failover, so it is not a suitable substitute for Multi-AZ.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-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 SOA-C02 exam.