What Interviewers Look for During a System Design Round at Amazon

System design interviews are a crucial part of Amazon’s tech hiring process, aimed at evaluating how you design large-scale systems.

For beginners, this open-ended round can be intimidating, and it's often unclear where to start or what to focus on.

One common misconception is that there’s a single “correct” design – in reality, Amazon cares more about your thought process, clarity, and decision-making.

The good news is interviewers don’t expect you to have built Amazon-scale systems before; they’re looking for solid fundamentals and a structured approach to problem-solving.

What Amazon Interviewers Evaluate

Amazon interviewers typically assess a core set of skills during the system design round. They are less interested in low-level coding details and more focused on high-level architecture and reasoning. Key areas include:

Clarifying Requirements

Before designing anything, start by clarifying the system’s requirements and constraints.

Interviewers want to see you gather information about the goals, features, and boundaries. This ensures you understand the problem space and avoids false assumptions.

Clearly identifying the functional and non-functional requirements up front shows structured thinking.

Scalability & Performance

Amazon’s systems serve millions of users, so scalability is a top concern.

Interviewers check whether your design can handle huge traffic and data volumes.

Discuss techniques like horizontal scaling (adding servers), load balancing, and caching to show you’re designing for performance.

They also care about latency and throughput – ensuring the system responds quickly to many requests per second.

Trade-offs & Decision Making

There’s no perfect design, so interviewers want to see you justify your choices. Every decision has trade-offs (e.g. SQL vs. NoSQL). Explain why you chose one approach and what you gain or lose by it. Weighing pros and cons aloud shows critical thinking.

Navigate complex system design tradeoffs.

Reliability & Fault Tolerance

Reliability is critical. Interviewers check if you design for failure scenarios and high availability.

Think about fault tolerance – what happens if a server crashes or an entire data center goes down? Good designs include redundancy and graceful degradation so the system continues to operate (even if in a reduced capacity) during failures.

Data Management & Storage

How you handle data is a major aspect of system design. Interviewers will assess your knowledge of databases, storage, and consistency. Choose an appropriate database solution (relational or NoSQL) and justify why it fits the use case. You might shard (split) the database to distribute load as data or traffic grows. Also decide if the system needs strong consistency or if eventual consistency is acceptable. Read strong consistency vs. eventual consistency.

API & Communication Design

Most modern systems consist of multiple services communicating via APIs or messaging.

Interviewers look at how you define service boundaries and interactions. Outline clear APIs for the major functions of your design. If you break it into microservices, explain how they communicate – maybe via REST calls or an async message queue.

The key is that each service has a well-defined purpose and interface. Describing a couple of core API endpoints and their roles shows you can design clean interfaces.

Recommended Courses

1. Grokking System Design Fundamentals
2. Grokking the System Design Interview
3. Grokking the Advanced System Design Interview
4. Grokking Amazon Coding Interview

How to Structure Your Response in a System Design Interview at Amazon

System design interviews are usually time-boxed (often around 45 minutes total, with ~30 minutes focused on design).

Managing your time and sticking to a structure ensures you cover all key points.

Here’s a possible timeline to organize your response:

• Minutes 1-5: Restate the problem and ask clarifying questions about requirements and constraints (both functional and non-functional). This ensures you start designing with the correct goals in mind.

• Minutes 5-10: Outline a high-level architecture – identify the major components (clients, servers, databases, etc.) and describe how data flows between them.

• Minutes 10-20: Pick a couple of critical components and dive deeper. For example, detail your database choice and design (schema, replication) or caching strategy, explaining how they meet the requirements.

• Minutes 20-25: Discuss how your design would scale under heavy load and how it handles failures. Highlight any trade-offs in your approach and how you would mitigate them.

• Minutes 25-30: Summarize the design, emphasizing how it meets the key requirements (like scalability and reliability). Finish by indicating you’re open to follow-up questions.

Common Mistakes and How to Avoid Them

• Failing to ask clarifying questions: Don’t start designing without fully understanding the problem. Always clarify the requirements and constraints first to make sure you’re solving the right problem.

• Ignoring scalability and high availability: A design that works on one machine will crumble at Amazon’s scale. Plan for growth (horizontal scaling) and eliminate single points of failure from the start.

• Not communicating your thinking: If you stay silent, the interviewer can’t follow your thought process. Talk through your ideas and decisions as you design.

• Overcomplicating the design: Adding every possible technology or microservice can backfire. Start with a simple design that meets the requirements, and only add complexity when it’s needed (with reasoning).

Check out Amazon Software Engineer Guide.

Final Thoughts & Key Takeaways

Remember, interviewers care more about how you approach the design than finding a “perfect” answer.

Even as a beginner, you can impress them by being structured, thoughtful, and communicative.

To wrap up, always begin by understanding the problem, design with scalability and reliability in mind, and articulate your decisions clearly. Treat the interview as a collaborative discussion, stay calm, and think out loud as you work through the design.

Key takeaways:

• Be structured and systematic: Break down the problem step-by-step (requirements → high-level design → details → evaluation).

• Prioritize scale and reliability: Design for millions of users and ensure the system stays available even if parts fail.

• Communicate and justify your choices: Explain your decisions and trade-offs clearly.