Top 10 AWS Solutions Architect Interview Questions (2026)

Welcome to the ultimate guide for cracking the AWS Solutions Architect interview in 2026. This guide is built to cover both foundational knowledge and real-world scenarios.

1. High Availability Architecture

Question: A client wants to deploy a highly available web application. They expect traffic spikes during the holidays. How would you design this?

Answer: The core of a highly available web application involves minimizing single points of failure:

1. Multi-AZ Deployment: Deploy the application across at least two Availability Zones (AZs).
2. Auto Scaling: Use an Auto Scaling Group (ASG) behind an Application Load Balancer (ALB).
3. Database: Use Amazon Aurora with multi-AZ read replicas.
4. Caching: Implement Amazon ElastiCache (Redis) to offload database query load.
5. CDN: Distribute static assets using Amazon CloudFront.

2. Security & Compliance

Question: How do you ensure an S3 bucket is secure and data cannot be accidentally deleted?

Answer: Security in S3 is a multi-layered approach:

• Block Public Access: Ensure "Block All Public Access" is checked.
• Bucket Policies: Require TLS (aws:SecureTransport) and enforce specific VPC endpoint access.
• Versioning & MFA Delete: Enable S3 Versioning and enforce MFA Delete.
• Encryption: Enable Default Encryption (SSE-KMS or SSE-S3).

3. Cost Optimization Strategies

Question: A company's EC2 costs have skyrocketed due to leaving instances running 24/7. How do you optimize this?

Answer:

1. Determine baseline usage and purchase Compute Savings Plans or Reserved Instances to save up to 72%.
2. Identify non-production environments and use AWS Instance Scheduler to shut them down at night/weekends.
3. Migrate stateless, fault-tolerant workloads to EC2 Spot Instances.
4. Right-size underutilized instances via AWS Compute Optimizer.

4. Disaster Recovery (DR)

Question: What is the difference between RTO and RPO, and what is the "Pilot Light" strategy?

Answer:

• RTO (Recovery Time Objective): Maximum acceptable downtime.
• RPO (Recovery Point Objective): Maximum acceptable data loss (e.g., 1 hour).
• Pilot Light Strategy: Running core services (like DBs) in standby mode in a DR region. In an event of a disaster, the rest of the application instances are rapidly provisioned/scaled around the Pilot Light to take over traffic.

5. Serverless Architectures

Question: Explain how AWS Lambda integrates with API Gateway and what "Cold Starts" are.

Answer: API Gateway acts as the entry door, routing HTTP requests to Lambda functions which dynamically scale and execute business logic. A "Cold Start" happens when Lambda is invoked after being idle, taking extra milliseconds to provision isolation environments. Cold starts can be mitigated by keeping functions "warm" via EventBridge pings or by enabling Provisioned Concurrency.

6. Database Migration Strategies

Question: How would you migrate a massive on-premise Oracle database to AWS with minimal downtime?

Answer: For minimal downtime and heterogenous migration (e.g. from Oracle to Aurora PostgreSQL), use AWS Schema Conversion Tool (SCT) to migrate the schema. Then, use AWS Database Migration Service (DMS) to continuously replicate data while keeping the source operational. Once they are fully synced, perform the application cutover.

7. Decoupling Patterns

Question: You need to decouple an order intake system from the order fulfillment processor. What services do you use?

Answer: Amazon SQS (Simple Queue Service) combined with Amazon SNS (Simple Notification Service). The intake system pushes an "order received" raw message to an SQS queue. The fulfillment workers poll the SQS queue, process the orders at their own pace without crashing under heavy loads, and then delete the messages securely.

8. Network Troubleshooting

Question: An EC2 instance in a private subnet cannot connect to the internet to download a patch. What might be wrong?

Answer:

1. It is missing a NAT Gateway in the Public Subnet.
2. The Private Subnet's Route Table does not point 0.0.0.0/0 towards the NAT Gateway.
3. The Security Group outbound rules do not allow HTTP/HTTPS out.
4. Network ACLs (NACLs) are blocking outbound traffic on ports 80/443 or inbound traffic on ephemeral return ports (1024-65535).

9. Caching Mechanisms

Question: When would you choose DynamoDB Accelerator (DAX) over Amazon ElastiCache (Redis)?

Answer: Choose DAX specifically when you need seamless, write-through caching purely for DynamoDB applications. It works without requiring any application-level caching logic rewrites. Choose ElastiCache when building custom caches for RDS databases, session stores, or when needing complex data structures (lists, string sets, geospatial data in Redis).

10. Multi-Account Management

Question: A large enterprise wants to isolate their billing and security boundaries across 50 different dev teams. How do you implement this?

Answer: Use AWS Organizations heavily. Create separate AWS accounts for every team/environment to guarantee perfect blast-radius isolation. Use AWS Control Tower to lay down standard security guardrails automatically. Consolidate their billing to the main payer account to leverage volume discounts using Consolidated Billing.

Summary

These are the core architectural paradigms tested in 2026. Download the complete PDF guide above to access the deep-dive architectural diagram templates perfectly tailored for your big interview!