Top 50 AWS Solutions Architect Interview Questions (2026)

Introduction

Landing an AWS Solutions Architect role requires more than just certification knowledge. Interviewers want to assess your practical experience, problem-solving abilities, and understanding of real-world architectural decisions. This guide covers the most commonly asked interview questions, organized by topic.

Compute & EC2 Questions

1. What's the difference between On-Demand, Reserved, and Spot instances?

Answer: On-Demand instances are pay-as-you-go with no commitment. Reserved Instances offer up to 72% discount for 1-3 year commitments. Spot Instances can save up to 90% but can be interrupted with 2-minute notice. Choose based on workload predictability and fault tolerance.

2. How would you design a highly available web application on AWS?

Answer: Use multiple Availability Zones with an Application Load Balancer distributing traffic across Auto Scaling groups. Deploy in at least 2 AZs, use RDS Multi-AZ for the database, store static assets in S3 with CloudFront, and implement health checks at every layer.

3. Explain EC2 placement groups and when to use each type.

Answer:

• Cluster: Low latency, high throughput (HPC, big data)
• Spread: Critical instances on separate hardware (max 7 per AZ)
• Partition: Large distributed workloads like Hadoop, Cassandra

4. What happens when an EC2 instance fails a health check behind an ALB?

Answer: The ALB stops routing traffic to the unhealthy instance. If Auto Scaling is configured, it will terminate the unhealthy instance and launch a replacement. The deregistration delay (default 300s) allows in-flight requests to complete.

5. How do you choose between EC2, Lambda, and ECS/Fargate?

Answer: EC2 for long-running workloads needing full OS control. Lambda for event-driven, short-duration tasks (<15 min). ECS/Fargate for containerized applications requiring consistent runtime environments without managing servers.

Storage Questions

6. Compare S3 storage classes and their use cases.

Answer:

• Standard: Frequently accessed data
• Intelligent-Tiering: Unknown/changing access patterns
• Standard-IA: Infrequent access, rapid retrieval needed
• One Zone-IA: Infrequent, recreatable data
• Glacier: Archive, minutes-hours retrieval
• Glacier Deep Archive: Long-term archive, 12-48 hour retrieval

7. How does S3 achieve 99.999999999% durability?

Answer: S3 automatically replicates data across a minimum of 3 Availability Zones within a region. It uses checksums to detect corruption and automatically repairs any detected issues. Cross-region replication can add another layer of protection.

8. When would you use EBS vs EFS vs S3?

Answer:

• EBS: Block storage for single EC2 instance, databases, boot volumes
• EFS: Shared file system across multiple instances, content management
• S3: Object storage for static content, backups, data lakes

9. Explain S3 versioning and how to protect against accidental deletion.

Answer: Versioning keeps multiple variants of an object. Enable MFA Delete to require MFA for permanent deletions. Use S3 Object Lock for WORM compliance. Lifecycle policies can transition old versions to cheaper storage classes.

10. What is S3 Transfer Acceleration and when would you use it?

Answer: Transfer Acceleration uses CloudFront edge locations to speed up uploads to S3. Use it when uploading from geographically distant locations. It can improve transfer speeds by 50-500% for long-distance transfers.

Networking & VPC Questions

11. Design a VPC for a three-tier web application.

Answer: Create public subnets for ALB/NAT Gateway, private subnets for application servers, and isolated subnets for databases. Use NACLs as stateless perimeter security and Security Groups for instance-level stateful filtering. Route tables direct traffic appropriately.

12. What's the difference between Security Groups and NACLs?

Answer: Security Groups are stateful (return traffic automatically allowed), operate at instance level, support allow rules only. NACLs are stateless (must explicitly allow return traffic), operate at subnet level, support allow and deny rules.

13. How does a NAT Gateway differ from a NAT Instance?

Answer: NAT Gateway is managed, highly available, scales automatically, and supports up to 45 Gbps. NAT Instance is self-managed, requires manual HA setup, limited by instance size. NAT Gateway is preferred for production workloads.

14. Explain VPC Peering vs Transit Gateway vs PrivateLink.

Answer:

• VPC Peering: 1:1 connection, non-transitive, works cross-region
• Transit Gateway: Hub-and-spoke for many VPCs, supports transitive routing
• PrivateLink: Expose services privately to other VPCs without crossing internet

15. How would you connect an on-premises data center to AWS?

Answer: Options include Site-to-Site VPN (quick, encrypted over internet), Direct Connect (dedicated connection, consistent latency), or Direct Connect + VPN (dedicated connection with encryption). Choose based on bandwidth, latency, and security requirements.

Database Questions

16. When would you choose RDS vs DynamoDB vs Aurora?

Answer:

• RDS: Traditional relational workloads, existing SQL applications
• DynamoDB: High-scale, low-latency NoSQL, unpredictable workloads
• Aurora: MySQL/PostgreSQL compatible with 5x performance, auto-scaling storage

17. Explain RDS Multi-AZ vs Read Replicas.

Answer: Multi-AZ provides synchronous replication to standby for HA/failover (same region). Read Replicas provide asynchronous replication for read scaling (can be cross-region). Multi-AZ is for availability; Read Replicas are for performance.

18. How does DynamoDB handle scaling?

Answer: DynamoDB offers On-Demand (auto-scales instantly, pay per request) or Provisioned capacity (set RCU/WCU with optional auto-scaling). Data is partitioned by primary key. Hot partitions can throttle performance, so design keys for even distribution.

19. What is Aurora Global Database and when would you use it?

Answer: Aurora Global Database replicates across regions with <1 second lag. Use for disaster recovery with RPO <1 second, serving global users with local read latency, or migrating from on-premises with minimal downtime.

20. How do you encrypt data at rest and in transit in RDS?

Answer: At rest: Enable encryption at creation using AWS KMS (cannot encrypt existing unencrypted DB). In transit: Enable SSL/TLS connections, enforce with rds.force_ssl parameter. Snapshots of encrypted DBs are also encrypted.

Security & IAM Questions

21. Explain the difference between IAM Users, Roles, and Policies.

Answer: Users are identities for people. Roles are identities for services/applications with temporary credentials. Policies are JSON documents defining permissions. Attach policies to users/roles to grant permissions.

22. What is the principle of least privilege and how do you implement it?

Answer: Grant only the minimum permissions needed. Use specific resource ARNs instead of wildcards. Implement conditions in policies. Regular access reviews using IAM Access Analyzer. Use Service Control Policies in Organizations for guardrails.

23. How do you secure cross-account access?

Answer: Create an IAM role in the target account with trust policy allowing the source account. Users assume the role using STS AssumeRole. Use external ID for third-party access. Define specific permissions in the role's policy.

24. Explain AWS Organizations and Service Control Policies.

Answer: Organizations manages multiple accounts centrally. SCPs set permission guardrails across accounts (deny only at organization level). Even account root users cannot exceed SCP boundaries. Use for compliance, security, and cost controls.

25. How would you detect and respond to compromised credentials?

Answer: Use GuardDuty for threat detection. Enable CloudTrail for API logging. Set up CloudWatch alarms for suspicious activity. Use IAM Access Analyzer for external access review. Respond by rotating credentials, revoking sessions, and investigating with Athena.

Architecture & Design Questions

26. Design a serverless architecture for a REST API.

Answer: API Gateway handles requests and authentication. Lambda functions process business logic. DynamoDB stores data. CloudWatch monitors performance. Use X-Ray for tracing. Implement API Gateway caching and Lambda Provisioned Concurrency for performance.

27. How do you implement a disaster recovery strategy on AWS?

Answer: Options by RTO/RPO:

• Backup & Restore: Cheapest, highest RTO (hours)
• Pilot Light: Core systems always running, scale up on disaster
• Warm Standby: Scaled-down full system running
• Multi-Site Active/Active: Lowest RTO/RPO, highest cost

28. How would you migrate a monolithic application to microservices?

Answer: Start with strangler fig pattern - gradually replace components. Identify bounded contexts. Use API Gateway for routing. Implement event-driven communication with SNS/SQS. Containerize with ECS/EKS. Use service mesh for observability.

29. Design a system that handles 1 million requests per second.

Answer: Use CloudFront for edge caching. Route 53 with latency-based routing. ALB across multiple AZs. Auto Scaling EC2 fleets or Lambda with reserved concurrency. DynamoDB with DAX for microsecond reads. ElastiCache for session/compute caching.

30. How do you optimize costs on AWS?

Answer: Right-size instances using Compute Optimizer. Use Reserved Instances and Savings Plans for predictable workloads. Spot for fault-tolerant workloads. S3 Intelligent-Tiering. Implement auto-scaling. Delete unused resources. Use Cost Explorer and Budgets for visibility.

Scenario-Based Questions

31. Your application is experiencing high latency. How do you troubleshoot?

Answer: Check CloudWatch metrics at each layer (ALB, EC2, RDS). Use X-Ray for distributed tracing. Analyze slow query logs. Check for CPU/memory constraints. Review network throughput. Consider caching with ElastiCache or CloudFront.

32. How would you handle a sudden 10x traffic spike?

Answer: Auto Scaling should handle compute. Ensure ALB can scale (pre-warm for predictable events). DynamoDB On-Demand or provisioned with auto-scaling. Add CloudFront if not present. Implement circuit breakers and graceful degradation.

33. A client needs 99.99% availability. What's your architecture?

Answer: Multi-AZ deployment across at least 3 AZs. Multi-region with Route 53 health checks and failover. Aurora Global Database or DynamoDB Global Tables. Eliminate single points of failure. Implement chaos engineering for validation.

34. How do you secure a public-facing API?

Answer: Use API Gateway with AWS WAF for protection. Implement authentication with Cognito or Lambda authorizers. Rate limiting and throttling. Enable CloudTrail logging. Use VPC endpoints for backend services. Implement input validation.

35. Design a real-time analytics pipeline.

Answer: Kinesis Data Streams ingests data. Kinesis Data Analytics processes in real-time. Lambda for transformations. Store in S3 for data lake, DynamoDB for hot data, Redshift for analytics. QuickSight for visualization.

Behavioral & Experience Questions

36. Describe a challenging architecture problem you solved.

Answer: Structure your response using STAR (Situation, Task, Action, Result). Focus on the trade-offs you considered, how you gathered requirements, and the business impact of your solution.

37. How do you stay current with AWS services?

Answer: AWS re:Invent sessions, AWS blogs, hands-on experimentation, AWS certifications, community events, and following AWS heroes on social media. Regular proof-of-concept projects with new services.

38. Tell me about a time you had to make a trade-off between cost and performance.

Answer: Discuss specific scenario, stakeholder communication, data-driven decision making, and outcome. Show understanding that architecture is about balancing competing concerns.

39. How do you handle disagreements with stakeholders about architecture decisions?

Answer: Focus on data and requirements. Create prototypes to demonstrate trade-offs. Document decisions and reasoning. Find common ground on business objectives. Escalate appropriately if consensus cannot be reached.

40. Describe your experience with infrastructure as code.

Answer: Discuss tools (CloudFormation, Terraform, CDK), benefits (repeatability, version control, documentation), challenges (state management, drift detection), and best practices (modules, testing, CI/CD integration).

Advanced Questions

41. How does AWS achieve global infrastructure resilience?

Answer: Regions are isolated (blast radius containment). AZs have independent power, cooling, networking. Local Zones bring services closer to users. Wavelength integrates with 5G networks. Global accelerator uses AWS backbone.

42. Explain the CAP theorem and how it applies to AWS services.

Answer: CAP states distributed systems can have two of: Consistency, Availability, Partition tolerance. DynamoDB chooses AP (eventually consistent by default). Aurora chooses CP. Understand trade-offs when designing systems.

43. How would you implement zero-downtime deployments?

Answer: Blue-green deployment with Route 53 or ALB weighted routing. Rolling updates with Auto Scaling. Canary deployments with CodeDeploy. Database migrations with expand-contract pattern. Feature flags for gradual rollouts.

44. What are the AWS Well-Architected Framework pillars?

Answer: Operational Excellence, Security, Reliability, Performance Efficiency, Cost Optimization, and Sustainability. Each pillar has design principles, best practices, and review questions to guide architecture decisions.

45. How do you implement observability in a distributed system?

Answer: Metrics with CloudWatch (custom metrics, dashboards, alarms). Logs centralized in CloudWatch Logs (structured JSON). Traces with X-Ray. Implement correlation IDs. Use CloudWatch ServiceLens for service maps.

Quick-Fire Technical Questions

46. What is the maximum size of an S3 object?

Answer: 5 TB. Single PUT limit is 5 GB; use multipart upload for larger objects.

47. What is the default timeout for a Lambda function?

Answer: 3 seconds. Maximum is 15 minutes.

48. How many subnets can you create per VPC?

Answer: 200 (soft limit, can be increased).

49. What is the difference between SQS Standard and FIFO queues?

Answer: Standard offers at-least-once delivery with best-effort ordering. FIFO guarantees exactly-once processing and strict ordering. FIFO has lower throughput (3,000 msg/s with batching).

50. What is the maximum number of tags you can assign to an AWS resource?

Answer: 50 tags per resource.

Additional Resources

• AWS Well-Architected Framework - Official AWS best practices
• AWS Architecture Blog - Real-world architecture patterns
• How to Pass the AWS Solutions Architect Associate Exam - Our comprehensive study guide
• AWS vs Azure vs GCP: Which Certification First? - Choosing your cloud path

Conclusion

Preparing for an AWS Solutions Architect interview requires both theoretical knowledge and practical experience. Focus on understanding the "why" behind architectural decisions, not just the "what." Be ready to discuss trade-offs, as there's rarely a single correct answer.

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