Three Actions to Improve High Availability for a Single EC2 Instance
A company is migrating a legacy application to AWS. The application runs on a single EC2 instance and uses an attached EBS volume for data storage. The company wants to improve high availability. Which THREE actions should the company take? (Choose three.)
Quick Answer
The three actions to improve high availability for a single EC2 instance are placing the instance behind an Application Load Balancer, using Auto Scaling across multiple Availability Zones, and implementing a Multi-AZ RDS database. This combination works because a single EC2 instance is a single point of failure; distributing compute across multiple AZs with Auto Scaling ensures that if one AZ fails, another instance takes over, while the ALB routes traffic only to healthy instances, and Multi-AZ RDS provides a synchronous standby replica for database durability. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your ability to decouple compute, storage, and database layers to eliminate single points of failure—a common trap is thinking a single EBS volume or instance store alone provides high availability, but they lack cross-AZ redundancy. Remember the memory tip: “ALB + ASG across AZs + Multi-AZ RDS” forms the three-legged stool of high availability for a legacy single-instance migration.
⚠ Common exam trap
SAP-C02 often tests the confusion between performance improvements (higher IOPS, instance store) and availability improvements (Multi-AZ, ASG across AZs, ALB), so candidates must map each option to the correct pillar.
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
✓
Migrate the database to Amazon RDS with Multi-AZ deployment.
Option A is correct because migrating the database to Amazon RDS with a Multi-AZ deployment provides automatic failover to a standby replica in a different Availability Zone, eliminating the single point of failure for data storage and improving availability. Option D is correct because placing the EC2 instance in an Auto Scaling group spanning multiple Availability Zones allows the application to be launched in more than one AZ and automatically replaced if an instance or AZ fails. Option E is correct because placing the EC2 instances behind an Application Load Balancer distributes incoming traffic across healthy targets in multiple AZs and routes around failed instances, which is essential for high availability. Option B is incorrect because increasing EBS IOPS only improves performance, not availability, and does not address single-instance or single-AZ failure. Option C is incorrect because instance store is ephemeral and tied to a single host, so it reduces durability and availability rather than improving it.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Migrate the database to Amazon RDS with Multi-AZ deployment.
Why this is correct
Migrating to Amazon RDS with Multi-AZ satisfies the high-availability constraint by replacing a single-instance database with a synchronously replicated standby in a second Availability Zone. Automatic failover redirects the endpoint during an AZ outage, eliminating the EBS volume's single point of failure without application connection-string changes.
- ✗
Use an EBS volume with higher IOPS to improve performance.
Why it's wrong here
Higher IOPS addresses disk throughput, not availability; a single EC2 instance and its EBS volume remain a single point of failure. Provisioned IOPS volumes suit I/O-intensive databases needing consistent latency, but they do nothing to remove the instance-level failure domain this scenario targets.
- ✗
Store data on the instance store instead of EBS to reduce latency.
Why it's wrong here
Instance store is ephemeral: data is lost on stop, termination, or host failure, which reduces durability rather than improving availability. It is chosen for temporary scratch data, buffers, or caches where sub-millisecond latency matters and persistence is irrelevant.
- ✓
Place the EC2 instance in an Auto Scaling group that spans multiple Availability Zones.
Why this is correct
An Auto Scaling group spanning multiple Availability Zones directly addresses the single-instance failure domain: if one AZ degrades, the group launches a replacement instance in a surviving AZ, restoring capacity without manual intervention. This satisfies the high availability requirement by removing the single EC2 instance as a single point of failure.
- ✓
Place the EC2 instances behind an Application Load Balancer.
Why this is correct
An Application Load Balancer distributes incoming traffic across multiple targets in different Availability Zones, removing the single point of failure at the entry tier. This directly satisfies the high-availability requirement by ensuring that if one EC2 instance fails, the ALB routes requests to healthy instances, though it must be paired with a multi-AZ Auto Scaling group.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Same concept, more angles
2 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 has a legacy monolithic application running on a single EC2 instance. The application stores customer data in an attached EBS volume. The company wants to modernize the application to improve scalability and availability. Which approach should a solutions architect recommend?
hard- A.Use a larger EC2 instance with enhanced networking.
- B.Configure multiple EC2 instances to share the same EBS volume using Multi-Attach.
- C.Replace the EBS volume with an Aurora RDS database.
- ✓ D.Refactor the application into microservices running on Amazon ECS with data stored in Amazon S3.
Why D: Migrating to a containerized, stateless application decouples storage and allows scaling. Option A is wrong because a larger instance still has a single point of failure. Option B is wrong because Multi-Attach EBS volumes have limited support and multiple instances writing to the same volume can cause data corruption. Option C is wrong because RDS is for databases, not for application data stored in files.
Variation 2. A company has a legacy application that runs on a single EC2 instance. The application stores data on an attached EBS volume. The company wants to improve availability and reduce the recovery time objective (RTO) in case of instance failure. What should the company do?
hard- ✓ A.Create an Auto Scaling group with a minimum of 2 instances across multiple Availability Zones and use a load balancer.
- B.Take frequent EBS snapshots and automate the creation of a new instance from the latest snapshot.
- C.Configure the EBS volume as a Multi-Attach volume and attach it to a standby instance.
- D.Convert the instance to an AMI and launch a new instance from that AMI in a different Availability Zone.
Why A: An Auto Scaling group with a minimum of two instances across multiple Availability Zones combined with a load balancer provides high availability and automatic failover, reducing RTO significantly. Option B is wrong: while EBS snapshots are useful for backups, restoring from a snapshot to create a new instance involves manual steps and can take minutes, not improving RTO adequately. Option C is wrong: Multi-Attach EBS volumes are for specific clustered applications (e.g., Windows Server Failover Clustering) and not all applications support it; also, it does not provide automatic failover. Option D is wrong: converting to an AMI and launching in another AZ requires manual intervention and does not ensure rapid recovery; it's a migration step, not an availability solution.
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.