In this article
The framework and the role
The design round often sits beside coding rounds; for that side, see the coding interview guide. The questions below are about choosing between designs.
What is the AWS Well-Architected Framework?
The framework describes AWS best practices and strategies to use when designing and operating a cloud workload (AWS Well-Architected Framework documentation, accessed October 2026). It is based on six pillars: operational excellence, security, reliability, performance efficiency, cost optimization and sustainability (AWS Well-Architected Framework, Reliability pillar, accessed October 2026). In an interview, use the pillars as a checklist when you critique a design: say which pillar a choice helps and which it hurts.
Why it is asked: it shows whether you judge designs against shared criteria or only name services. Read the full explanation: AWS Well-Architected Framework documentation.
Is Well-Architected a certification or a product?
Well-Architected is a framework, not a certification or a product. AWS groups a framework, domain-specific lenses and a self-service assessment tool under that one name (AWS, Well-Architected, accessed October 2026), and offers the Well-Architected Tool at no charge, a service for reviewing and measuring a workload against the framework (AWS Well-Architected Framework documentation, accessed October 2026). The certification is a separate thing: the Solutions Architect Associate exam validates a candidate's ability to design solutions based on the framework (AWS exam guide, accessed October 2026).
Why it is asked: candidates often blur the framework, the tool and the exam. Read the full explanation: AWS Well-Architected Framework documentation.
What does the Solutions Architect Associate exam cover, and how should I split study time?
The exam guide lists four domains with these shares of scored content: secure architectures 30%, resilient architectures 26%, high-performing architectures 24% and cost-optimized architectures 20%, which sum to 100% (AWS exam guide, accessed October 2026). As an illustrative split of a 40-hour plan, proportional time is 12, 10.4, 9.6 and 8 hours.1 The weights describe the exam, not any interview.
Why it is asked: it checks whether you know what the role is measured on. Read the full explanation: AWS exam guide.
How do you answer a design question that has no single right answer?
Name the requirements first, then two candidate designs, then compare them against the pillars and pick one, saying what you give up. Every domain title in the exam guide begins with "Design", which points to the skill being tested: choosing between designs, not reciting service facts (AWS exam guide, accessed October 2026). A strong answer ends with the trade-off in one sentence.
Why it is asked: interviewers want reasoning they can follow and challenge. Read the full explanation: AWS exam guide.
How do you gather requirements and handle a design disagreement?
Ask stakeholders for non-functional requirements as measurable targets: availability, recovery time and recovery point, latency, security and budget. Write them down and get them confirmed. In a disagreement, compare each option against those targets and the pillars, say what each one gives up, and let the agreed targets, not seniority, decide.
Why it is asked: it shows you turn opinions into criteria. Read the full explanation: AWS Well-Architected Framework documentation.
Availability and resilience
What is the difference between high availability and fault tolerance?
Availability is the share of time a system is working and reachable. High availability means designing to keep downtime low, for example by removing single points of failure. Fault tolerance is the stricter property of continuing to operate without interruption when a component fails, which usually costs more. The exam guide lists the two together as one task, "highly available and/or fault-tolerant" (AWS exam guide, accessed October 2026).
Why it is asked: the terms are often used as synonyms, and the gap shows depth. Read the full explanation: AWS exam guide.
How much downtime does 99.9% availability allow?
A year has 525,600 minutes, so 99.9% availability allows 525.6 minutes, about 8.76 hours, of downtime per year.1 At 99.95% it is 262.8 minutes, at 99.99% it is 52.56 minutes, and at 99.999% it is 5.256 minutes.1 Each extra nine divides the budget by ten, and each nine usually costs more redundancy.
Text description of the diagram
- A year has 525,600 minutes, so 99.9% availability allows 525.6 minutes of downtime per year.
- At 99.99% it is 52.56 minutes, and at 99.999% it is 5.256 minutes.
Why it is asked: it tests whether you can turn a target into a number.
What happens to availability when you chain or duplicate components?
Chained components multiply: three in series, each at 99.9%, give 99.7003% overall, about 26.25 hours of downtime per year.1 Two duplicates in parallel, each at 99.9%, give 99.9999%, about 0.5256 minutes per year, but only if failures are independent and failover is instant and never fails itself.1 A shared database or a shared network path breaks the independence assumption, so name the shared dependencies.
Why it is asked: it separates arithmetic from slogans about redundancy. Read the full explanation: AWS Well-Architected Framework, Reliability pillar.
What are RTO and RPO, and how do they shape a disaster recovery design?
The recovery time objective (RTO) is how long an outage may last before service must return. The recovery point objective (RPO) is how much recent data you can afford to lose. Ask the business for both, then choose a strategy that meets them at acceptable cost: backup and restore, pilot light, warm standby or multi-site active/active, which are typically ordered from lower cost and complexity to higher cost and faster recovery.
Why it is asked: it shows you start from business needs, not tools. Read the full explanation: AWS whitepaper, Disaster recovery options in the cloud.
When would you use read replicas?
Use them when a database is read-heavy: replicas serve reads and leave the primary free for writes. The exam guide lists "When to use read replicas" as a topic (AWS exam guide, accessed October 2026). The trade-off is replication lag, so a replica can return slightly stale data. Check what your database service does on failure before you count a replica as a standby.
Why it is asked: it tests scaling reads and the consistency cost together. Read the full explanation: AWS exam guide.
Knowing it is half the job. Saying it is the other half.
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What is the difference between object, file and block storage?
The exam guide lists storage types with their characteristics, naming object, file and block (AWS exam guide, accessed October 2026). Object storage holds whole items addressed by a key and suits backups, media and static content. File storage presents a shared directory tree many servers can mount. Block storage is a raw volume, like a disk, usually attached to one server and used for databases and boot drives.
Why it is asked: matching storage to access pattern is a daily architect decision. Read the full explanation: AWS exam guide.
How do you choose a database for a new system?
Start from access patterns, not product names: what the reads and writes look like, how much consistency the business needs, how large the data will grow and who will operate it. Then name two candidates, such as a relational and a key-value store, and say what each gives up. A strong answer also says how you would migrate if the first guess proves wrong.
Why it is asked: it reveals whether requirements drive your choice. Read the full explanation: AWS exam guide, high-performing architectures domain.
Scaling, caching and networking
How do you scale a stateless web tier?
Put identical servers behind a load balancer and let an auto scaling group add or remove them as demand changes. This works because a stateless server keeps no user data of its own, so any server can handle any request; session data goes to a shared store. The trade-off is that scaling out needs health checks and warm-up time, so a sudden spike can still outrun it.
Why it is asked: it tests whether you design for elastic demand. Read the full explanation: AWS exam guide.
Where do you cache, and what does caching cost?
Cache close to the user with a content delivery network (CDN) for static content, and close to the database with an in-memory cache for repeated reads. Both cut latency and database load. The cost is staleness: a cached copy can be out of date, so set an expiry that matches how stale the business can tolerate and decide how you will invalidate it.
Why it is asked: it tests performance thinking and awareness of consistency cost. Read the full explanation: AWS exam guide.
How do you design the network for a public web application?
Put only what must be reachable, such as the load balancer, in public subnets, and keep application servers and databases in private subnets. Internet traffic reaches the public tier through an internet gateway, while private servers reach out through a managed network address translation (NAT) service. Restrict each layer so it accepts traffic only from the layer before it.
Why it is asked: it checks that you understand how traffic flows and where the boundaries are. Read the full explanation: AWS exam guide.
How do you move an existing workload to the cloud?
Start by deciding, per workload, whether to move it as it is or to re-architect it. Moving as it is is faster and carries the old design's limits. Re-architecting takes longer but can use elastic scaling and managed services. Then plan the data transfer: how much data there is, how long the copy takes over the available network, and how you will switch over and roll back with little downtime. The exam guide lists migration and data transfer in scope (AWS exam guide, accessed October 2026).
Why it is asked: it tests whether you weigh speed against long-term fit. Read the full explanation: AWS exam guide.
Integration and application design
What is loose coupling and why does it matter?
Loose coupling is a design in which components talk through narrow interfaces, such as queues or events, so one can fail, scale or change without breaking the others. The exam guide lists loose coupling and scalability among its topics (AWS exam guide, accessed October 2026). The cost is extra moving parts and harder debugging across services.
Why it is asked: it links design style to reliability and scale. Read the full explanation: AWS exam guide.
How do you choose between event-driven, microservice and multi-tier designs?
The exam guide names all three (AWS exam guide, accessed October 2026). A multi-tier design splits presentation, logic and data layers and is simple to reason about. Microservices split by business capability so teams deploy independently, at the price of network calls and operational load. Event-driven designs react to messages, which decouples producers from consumers but makes flow harder to trace. Pick by team size and change rate.
Why it is asked: it checks that you weigh organization as well as technology. Read the full explanation: AWS exam guide.
When would you put a queue between two services?
Put a queue, such as Amazon Simple Queue Service (SQS), between them when the producer can be faster than the consumer or when either side may be down. The queue absorbs bursts and lets failed work be retried. The trade-offs are asynchronous results and possible duplicate delivery, so consumers should be idempotent, meaning that handling the same message twice gives the same outcome.
Why it is asked: it is the standard test of decoupling in practice. Read the full explanation: AWS exam guide.
What do API Gateway, Step Functions, ECS and EKS do?
The exam guide names these services (AWS exam guide, accessed October 2026). Amazon application programming interface (API) Gateway is a managed front door for application programming interface (API) requests. Step Functions coordinates a multi-step workflow with retries. Elastic Container Service (ECS) and Elastic Kubernetes Service (EKS) run containers. In an interview, say what problem each solves before naming it.
Why it is asked: it separates service lists from understanding of their roles. Read the full explanation: AWS exam guide.
Security and cost
How do you design a secure architecture?
Security is the largest domain of the associate exam at 30% of scored content (AWS exam guide, accessed October 2026), and security is also a Well-Architected pillar. A strong answer covers least-privilege access, encryption in transit and at rest, network layers, and logging that lets you investigate. State which data is most sensitive and protect that first.
Why it is asked: it checks that security is designed in, not added last. Read the full explanation: AWS Well-Architected Framework, Security pillar.
How do you reduce the cost of an architecture without hurting it?
Cost optimization is one of the six pillars (AWS Well-Architected Framework, Reliability pillar, accessed October 2026), and the exam gives it 20% of scored content. Measure first, then right-size resources, match storage type to access pattern, and scale with demand. Say what a saving costs in reliability or latency, because a cut that breaks an availability target is not a saving.
Why it is asked: it tests judgment about trade-offs between pillars. Read the full explanation: AWS Well-Architected Framework documentation.
Follow-up questions
What are the common solution architect interview questions?
They cluster around the topics above: requirements and trade-offs, availability and recovery, storage and data, loose coupling and integration, security and cost. Practice saying a design aloud in this order, with one trade-off per choice. For the networking side of the loop, see the networking question list.
What are the AWS interview questions for solution architect?
They follow the exam topics: the Well-Architected pillars, high availability against fault tolerance, storage types, read replicas, and services such as API Gateway, queues, containers and workflows. Interviewers can ask these in any order; the exam guide is the most reliable outline of the topics.
What are cloud solution architect interview questions for Azure or Google Cloud?
The design reasoning carries over: requirements, availability math, storage fit, decoupling, security and cost. Service names and framework pillars differ by vendor, so read each vendor's own architecture documentation before the round; this page's sourced facts are about AWS only.
What are Java solution architect interview questions?
Expect the design questions here plus questions on the language and frameworks your architecture would use. Prepare with the Java question list and the Spring Boot question list, and for service-to-service calls review networking questions.
What do solution architect system design interview questions look like?
Typically one open prompt, such as designing a service for a given load, followed by probes on availability, data and cost. Clarify requirements, sketch components, do the availability arithmetic from the worked entries above, and name the trade-off. Breadth across the stack helps, as in full stack questions and system administration questions.
- Treat the six Well-Architected pillars as a checklist for judging any design.
- Design questions test choosing between options and stating the trade-off.
- Convert availability targets to minutes per year, and remember that chained components multiply.
- Ask for the recovery time and recovery point objectives before choosing a recovery strategy.
- Match storage, integration style and cost to the stated requirements, not to a service list.
Sources
- AWS Well-Architected (Architecture Center overview) — Amazon Web Services (accessed 2026-10-26; page undated), 26 Oct 2026
- AWS Well-Architected Framework (documentation) — Amazon Web Services (accessed 2026-10-26; page undated), 26 Oct 2026
- AWS Certified Solutions Architect – Associate (SAA-C03) Exam Guide — AWS Training and Certification (accessed 2026-10-26; document undated), 26 Oct 2026
- AWS Well-Architected Framework: Reliability Pillar — Amazon Web Services (accessed 2026-10-26; page undated), 26 Oct 2026
- AWS Well-Architected Framework: Security Pillar — Amazon Web Services (accessed 2026-10-26; page undated), 26 Oct 2026
- Disaster recovery options in the cloud (Disaster Recovery of Workloads on AWS) — Amazon Web Services (accessed 2026-10-26; page undated), 26 Oct 2026
