Top 30 AWS Solutions Architect Interview Questions and Answers
Landing a role as an AWS Solutions Architect requires more than just holding the certification. Interviewers want to see that you can apply architectural thinking to real-world problems, communicate trade-offs clearly, and design systems that balance performance, cost, security, and reliability. This guide covers 30 of the most commonly asked interview questions across six core categories, along with detailed answers and tips on what interviewers are really looking for.
Whether you are preparing for your first cloud architecture role or moving into a senior position, these questions will help you sharpen your thinking and articulate your knowledge with confidence. If you are also studying for the AWS Solutions Architect Associate exam, many of these topics overlap directly with SAA-C03 domains.
Architecture Design Questions
1. How would you design a highly available web application on AWS?
Walk through a multi-AZ architecture: Application Load Balancer across two or more AZs, EC2 instances in an Auto Scaling group, RDS Multi-AZ for database failover, static assets in S3 served through CloudFront.
What interviewers look for: Layered thinking (presentation, application, data) and understanding of AWS availability constructs.
2. A client needs a disaster recovery solution with an RTO of 15 minutes. What approach would you recommend?
A warm standby strategy fits a 15-minute RTO. Maintain a scaled-down but functional copy of production in a secondary region. Use Route 53 health checks with DNS failover and RDS cross-region read replicas that can be promoted to primary.
What interviewers look for: Understanding of the four DR strategies (backup/restore, pilot light, warm standby, multi-site) and matching them to RTO/RPO requirements.
3. How do you decide between a monolithic architecture and microservices on AWS?
This is about trade-offs. Monoliths are simpler to develop and deploy, ideal for small teams. Microservices offer independent scaling and deployment but introduce complexity in service discovery and data consistency. On AWS, microservices leverage ECS/EKS, API Gateway, SQS/SNS, and X-Ray. The choice depends on team size, scale, release velocity, and domain complexity.
What interviewers look for: Pragmatic thinking rather than dogmatic preference, weighing pros and cons based on business context.
4. How would you migrate a large on-premises database to AWS with minimal downtime?
Use AWS Database Migration Service (DMS) for continuous replication. Start with a full load migration followed by ongoing change data capture (CDC) to keep the source and target in sync. During the cutover window, stop writes to the source, let DMS catch up, then redirect the application to the new RDS or Aurora instance. For very large databases, consider using AWS Snowball for the initial data transfer, then DMS for ongoing replication.
What interviewers look for: Knowledge of migration tools, understanding of CDC concepts, and awareness of strategies to minimize downtime during cutovers.
5. How would you design a system that processes millions of events per day?
A common pattern uses Amazon Kinesis Data Streams or Amazon MSK for ingesting high-throughput event data. Consumers can be Lambda functions for real-time processing or Kinesis Data Firehose for loading into S3 or Redshift. For batch analytics, store raw events in S3, catalog them with Glue, and query with Athena. If the system needs sub-second processing, consider Kinesis Data Analytics or Flink on Amazon Managed Service for Apache Flink.
What interviewers look for: Experience with event-driven architectures and familiarity with the streaming and analytics ecosystem on AWS.
Networking Questions
6. Explain the difference between security groups and NACLs.
Security groups are stateful firewalls at the instance level supporting allow rules only. NACLs are stateless firewalls at the subnet level supporting both allow and deny rules, evaluated in order by rule number. Security groups handle primary access control; NACLs provide defense in depth. For more detail, see our VPC guide.
What interviewers look for: Clear understanding of stateful vs stateless and how they complement each other.
7. How would you connect an on-premises data center to AWS securely?
There are two primary options. AWS Site-to-Site VPN creates an encrypted tunnel over the public internet, suitable for moderate bandwidth needs and quick setup. AWS Direct Connect provides a dedicated physical connection with more consistent latency and higher throughput, ideal for large data transfers or latency-sensitive workloads. For maximum reliability, combine Direct Connect with a VPN as a backup path.
What interviewers look for: Knowledge of hybrid connectivity options and the ability to recommend based on bandwidth, latency, cost, and reliability requirements.
8. What is VPC peering and when would you use it instead of Transit Gateway?
VPC peering creates a direct network route between two VPCs. It is simple, has no bandwidth bottleneck, and works across accounts and regions. However, peering is not transitive, so connecting many VPCs creates a complex mesh. Transit Gateway acts as a central hub for connecting multiple VPCs, VPN connections, and Direct Connect gateways. Use peering for simple two-VPC connections and Transit Gateway when managing many VPCs or requiring centralized routing control.
What interviewers look for: Understanding of when simplicity (peering) wins over flexibility (Transit Gateway) and awareness of scaling considerations.
9. How do you ensure private resources can access the internet without being publicly accessible?
Place resources in a private subnet with a route to a NAT Gateway in a public subnet. The NAT Gateway allows outbound internet access for updates and patches while preventing inbound connections from the internet. For accessing AWS services without internet traffic, use VPC endpoints, either Gateway endpoints for S3 and DynamoDB or Interface endpoints for other services.
What interviewers look for: Solid grasp of public/private subnet design and the role of NAT Gateways and VPC endpoints.
10. How would you design a multi-region application with low latency for global users?
Use Route 53 with latency-based routing to direct users to the nearest region. Deploy the application stack in multiple regions behind regional ALBs. For static content, use CloudFront with edge locations worldwide. For the data layer, consider DynamoDB Global Tables for multi-region active-active or Aurora Global Database for read-heavy workloads with a primary write region and low-latency read replicas in secondary regions.
What interviewers look for: Ability to design globally distributed systems and understanding of data replication trade-offs (consistency vs latency).
Security Questions
11. How do you implement least privilege access in AWS?
Start by creating IAM policies that grant only the specific permissions needed for each role. Use AWS managed policies as a baseline, then scope down with custom policies. Implement permission boundaries to set maximum permissions for IAM entities. Use service control policies (SCPs) in AWS Organizations to set guardrails across accounts. Regularly audit permissions with IAM Access Analyzer and remove unused access. Never use the root account for daily operations, and always enable MFA.
For a comprehensive look at IAM for the SAA-C03 exam, check our IAM guide.
What interviewers look for: A systematic approach to access management beyond just “use IAM roles.” They want to see layered security thinking.
12. How would you encrypt data at rest and in transit on AWS?
For data at rest, use AWS KMS to manage encryption keys. S3 supports server-side encryption with SSE-S3, SSE-KMS, or SSE-C. RDS and EBS support encryption at creation time using KMS keys. For data in transit, enforce TLS/HTTPS for all API calls and application traffic. Use ACM to provision and manage SSL/TLS certificates. For VPN connections, IPsec encryption is applied automatically. Ensure load balancers terminate TLS and re-encrypt traffic to backend instances.
What interviewers look for: Knowledge of encryption options across services, understanding of key management, and awareness that encryption must cover both storage and network layers.
13. What steps would you take if you discovered compromised IAM credentials?
Immediately deactivate the compromised access keys. Review CloudTrail logs for unauthorized actions. Check for resources created during the compromise (EC2 instances, IAM users, security group changes). Rotate all credentials and implement preventive measures: MFA enforcement, temporary credentials via roles, and secret scanning.
What interviewers look for: Incident response methodology and knowledge of CloudTrail for forensics.
14. How do you secure an S3 bucket that stores sensitive data?
Block all public access using the S3 Block Public Access settings at the account and bucket level. Enable server-side encryption with SSE-KMS for audit trails on key usage. Use bucket policies to restrict access to specific IAM roles or VPC endpoints. Enable versioning to protect against accidental deletion. Turn on S3 access logging and use CloudTrail data events for monitoring. Consider using S3 Object Lock for regulatory compliance where data must be immutable.
For more on S3 security and storage concepts, see our S3 guide for the SAA-C03.
What interviewers look for: Defense-in-depth approach with multiple layers of protection, not just a single control.
15. How do you manage secrets in AWS applications?
Use AWS Secrets Manager for database credentials, API keys, and other secrets. Secrets Manager supports automatic rotation, which reduces the risk of stale credentials. For application configuration that is not sensitive, use AWS Systems Manager Parameter Store. Never hardcode secrets in application code, environment variables visible in the console, or version control. For Lambda functions, reference secrets at runtime rather than passing them as environment variables.
What interviewers look for: Understanding of secrets management as a practice, not just knowledge of the Secrets Manager service.
Database Questions
16. When would you choose DynamoDB over RDS?
Choose DynamoDB for applications requiring single-digit millisecond response times at any scale, key-value or document access patterns, and variable traffic with unpredictable spikes (using on-demand capacity). Choose RDS when you need complex joins, transactions across multiple tables, or when your application relies on a relational data model. DynamoDB excels for gaming leaderboards, session stores, IoT data, and shopping carts. RDS fits financial applications, ERP systems, and applications with complex reporting needs.
What interviewers look for: Understanding that database selection depends on access patterns, not just personal preference, and the ability to match services to use cases.
17. Explain the difference between RDS Multi-AZ and Read Replicas.
Multi-AZ is a high availability feature. AWS maintains a synchronous standby replica in a different AZ. If the primary fails, DNS automatically fails over to the standby. The standby is not accessible for reads. Read Replicas are for performance scaling. They use asynchronous replication and can serve read traffic, reducing load on the primary. Read Replicas can be in the same region or cross-region and can be promoted to standalone databases.
What interviewers look for: Clear distinction between availability (Multi-AZ) and performance (Read Replicas) and when to use each or both together.
18. How would you design a database layer for a globally distributed application?
For NoSQL workloads, DynamoDB Global Tables provide multi-region, active-active replication with eventual consistency. For relational workloads, Aurora Global Database offers a primary region for writes and up to five secondary regions for low-latency reads with typical replication lag under one second. If the application requires strong consistency for writes, designate a single write region and route writes there using Route 53 or application-level logic.
What interviewers look for: Awareness of global data replication options and understanding of consistency trade-offs in distributed databases.
19. When would you use ElastiCache and which engine would you choose?
Use ElastiCache when you need to reduce database load for read-heavy workloads, store session data, or implement leaderboards and counters. Choose Redis for complex data structures (sorted sets, lists, hashes), persistence, replication, and pub/sub messaging. Choose Memcached for simple key-value caching with multi-threaded performance and the ability to scale out by adding nodes. Redis is the more common choice due to its richer feature set.
What interviewers look for: Understanding of caching patterns and the ability to choose between Redis and Memcached based on requirements.
20. How do you handle database migrations when moving to a different engine?
Use AWS Schema Conversion Tool (SCT) to convert the schema and AWS Database Migration Service (DMS) for data migration with minimal downtime using change data capture. Test thoroughly in staging, especially stored procedures and queries that may behave differently on the new engine.
What interviewers look for: Awareness that schema conversion and data migration are separate challenges requiring different tools.
Compute Questions
21. How do you choose between EC2, ECS, EKS, and Lambda?
Choose EC2 for full OS control or hard-to-containerize applications. Choose ECS or EKS for containerized microservices; ECS is simpler while EKS suits multi-cloud Kubernetes strategies. Choose Lambda for event-driven, short-running tasks with zero server management. Consider cost: Lambda is cheapest for sporadic workloads, while EC2 Reserved Instances win for steady-state.
What interviewers look for: Pragmatic service selection based on workload characteristics rather than defaulting to one option.
22. Explain EC2 pricing models and when to use each.
On-Demand instances offer pay-per-second pricing with no commitment, ideal for unpredictable workloads or short-term testing. Reserved Instances provide up to 72% savings for one or three-year commitments, best for steady-state workloads. Savings Plans offer similar discounts with more flexibility across instance families. Spot Instances offer up to 90% savings but can be interrupted with two minutes notice, suitable for fault-tolerant batch processing, CI/CD workloads, and data analysis. Dedicated Hosts provide physical servers for licensing compliance.
What interviewers look for: Ability to optimize costs through instance pricing strategies and match pricing models to workload patterns.
23. How does Auto Scaling work and what scaling policies would you use?
Auto Scaling adjusts EC2 capacity based on defined conditions. Target tracking policies maintain a specific metric (like 70% average CPU utilization) by automatically scaling in or out. Step scaling policies add or remove different numbers of instances based on alarm thresholds. Scheduled scaling adjusts capacity at predictable times. Predictive scaling uses machine learning to forecast demand and pre-scale. For most applications, target tracking on CPU or request count per target is the simplest starting point.
What interviewers look for: Practical knowledge of scaling policies and the ability to select the right policy for different traffic patterns.
24. When would you use AWS Lambda vs. AWS Fargate?
Lambda is ideal for event-driven functions that run for under 15 minutes, need minimal runtime configuration, and scale to zero when idle. Fargate suits longer-running containerized applications that need more memory (up to 120 GB vs. Lambda’s 10 GB), custom runtimes, or persistent processes. Fargate also works better for applications with steady traffic since it avoids cold starts. Lambda shines for API backends, file processing triggers, and scheduled tasks.
What interviewers look for: Understanding of serverless compute options and the boundary conditions where each service excels.
25. How do you troubleshoot a slow-performing EC2 instance?
Check CloudWatch metrics for CPU, memory (requires agent), disk I/O, and network. High CPU may need a larger instance; high disk I/O may need provisioned IOPS. Check for T-series burstable credit exhaustion. Use OS-level tools (top, iostat) for deeper diagnostics.
What interviewers look for: Systematic troubleshooting methodology and knowledge of instance performance characteristics.
Cost Optimization Questions
26. How would you reduce AWS costs for a production workload by 30%?
Start with Cost Explorer to identify top cost drivers. Right-size instances using Compute Optimizer. Convert stable workloads to Reserved Instances or Savings Plans. Use S3 lifecycle policies for infrequently accessed data. Delete unused resources (unattached EBS, idle load balancers). Use Spot for batch workloads and auto scaling to match demand.
What interviewers look for: A methodical approach starting with data analysis and applying multiple strategies.
27. How do you prevent unexpected AWS bills?
Set up AWS Budgets with alerts at 50%, 80%, and 100% of spend. Enable Cost Anomaly Detection. Use SCPs to restrict expensive services in non-production accounts. Tag all resources for cost allocation. Automate dev environment shutdown schedules.
What interviewers look for: Proactive cost governance rather than reactive bill management.
28. A client is spending too much on data transfer. How would you optimize?
Analyze data transfer flows in Cost Explorer. Use CloudFront to reduce origin transfers. Keep traffic within the same AZ (free). Use VPC endpoints instead of NAT Gateways for AWS service access. Compress data before transfer and consider keeping data local to consumers.
What interviewers look for: Awareness that data transfer is often overlooked and knowledge of specific optimization techniques.
29. How do you choose between S3 storage classes to optimize costs?
Use S3 Standard for frequently accessed data. S3 Standard-IA for data accessed less than once a month but requiring rapid retrieval. S3 One Zone-IA when you can tolerate single-AZ durability risk. S3 Intelligent-Tiering when access patterns are unpredictable, as it automatically moves objects between tiers. S3 Glacier Instant Retrieval for archival data needing millisecond access. Glacier Flexible Retrieval for archives where minutes to hours retrieval is acceptable. Glacier Deep Archive for long-term compliance data accessed once or twice a year.
For a detailed comparison of S3 storage classes, see our S3 guide for the SAA-C03 exam.
What interviewers look for: Practical understanding of the storage class hierarchy and the ability to map access patterns to the right tier.
30. How would you design a cost-effective development environment?
Use smaller instances than production. Schedule start/stop for dev instances during business hours only (65% savings). Use Spot for CI/CD. Single-AZ database deployments. Tag resources and set per-team budget alerts.
What interviewers look for: Applying different standards based on environment while maintaining usability.
Tips for Whiteboard Architecture Sessions
Many Solutions Architect interviews include a whiteboard session where you are asked to design a system on the spot. Here are strategies to excel in these exercises.
Start with Requirements
Before drawing anything, clarify requirements: expected traffic, latency needs, consistency, compliance, and budget. This shows you think before you build.
Draw in Layers
Structure your diagram in layers: users/DNS, load balancing, application tier, caching, database, and storage. This demonstrates organized architectural thinking.
Explain Trade-offs
For every decision, explain why you chose it over alternatives. “I chose Aurora here because the application needs complex joins” is far more impressive than just drawing a database icon.
Address Cross-Cutting Concerns
After the core design, proactively discuss security, monitoring, cost optimization, and disaster recovery. This shows senior-level thinking.
Think Out Loud
Narrate your thought process. Interviewers evaluate how you think, not just what you draw.
Common Follow-Up Questions
Be prepared for these probing follow-ups after any answer:
- “What happens if that component fails?”
- “How would this scale to 10x the traffic?”
- “How would you reduce the cost by half?”
- “What security risks exist in this design?”
- “How would you monitor this system?”
Prepare with Practice
Studying for the AWS Solutions Architect Associate certification and practicing interview questions go hand in hand. The architectural thinking required for the SAA-C03 exam directly translates to interview performance.
To build exam-ready confidence and sharpen your understanding of AWS services, try Sailor.sh’s SAA-C03 mock exams. The scenario-based questions mirror both exam and interview formats, and detailed explanations help you understand the reasoning behind each architectural decision.
For more preparation resources, check out our study plan and exam tips.
Frequently Asked Questions
How many AWS services should I know for a Solutions Architect interview?
You should have deep knowledge of 15 to 20 core services (EC2, S3, RDS, DynamoDB, Lambda, VPC, IAM, CloudFront, Route 53, SQS, SNS, ECS, EKS, CloudWatch, KMS, ELB, Auto Scaling, Aurora) and working familiarity with another 20 to 30 services. Interviewers value depth over breadth.
Do I need the AWS Solutions Architect certification to get an architect role?
While not strictly required, the certification significantly strengthens your candidacy. It validates your knowledge and shows commitment to the platform. Many employers list it as preferred or required. See our salary guide for how certification impacts compensation.
How technical are Solutions Architect interviews compared to developer interviews?
They focus more on system design and trade-off analysis than coding. However, many include scripting questions around infrastructure as code with CloudFormation or Terraform.
Should I prepare differently for associate-level vs senior architect roles?
Yes. Associate-level interviews focus on service knowledge and best practices. Senior roles expect discussion of organizational strategy, complex multi-account architectures, migration planning, and cost governance with ambiguous scenarios.
What is the best way to practice for whiteboard sessions?
Design common systems (e-commerce, real-time dashboards, file processing pipelines) in 30-45 minute sessions. Have someone act as interviewer with follow-up questions. Review AWS architecture reference diagrams for patterns.