Last Updated on November 29th, 2025

Basic knowledge of System design is expected in technical hiring process even from junior software engineering roles. Unlike coding interviews that focus on algorithms and data structures, system design interviews evaluate a candidate’s ability to architect scalable, efficient, and maintainable software systems.

In today’s world, where applications must support millions of users, handle large volumes of data, and provide high availability, companies look for engineers who understand basics of system design, role of a system designer, microservices architecture, scalability, maintainability, availability, caching, and more. These interviews help assess whether candidates can balance trade-offs between scalability, reliability, performance, and cost.

If you want to refresh concepts of System Design first, kindly visit a series of articles on System Design Tutorials.

You may also need to check: How to prepare System Design Interviews for Beginner to Expert

Who will benefit from this System Design Practice Set?

This System Design Practice Set is created to help a wide range of learners and professionals. Here’s a breakdown of who will benefit the most:

1. Beginners in System Design: Those who are new to system design concepts, will find these MCQs incredibly helpful. It introduces concepts in a structured, question-driven format, that will help learners to gradually build their understanding through practical examples and detailed explanations.

2. Software Developers Preparing for Interviews: Whether you’re a Java developer, backend engineer, or full-stack developer, system design is a key component of technical interviews at top companies. Practicing these MCQs will help sharpen problem-solving skills, clarify system architecture trade-offs, and prepare candidates for L4–L6 level interviews at companies like Google, Amazon, Microsoft, Meta, and startups.

3. Professionals Transitioning to System Architect or Tech Lead Roles: If you’re a developer aiming to grow into a technical leadership or architectural role, these practice questions offer a strong foundation to start thinking at a system-level perspective.

4. Students and Learners in Computer Science Stream: Computer Science students looking to go beyond theoretical concepts will find this set a practical supplement to classroom learning. Especially useful for capstone projects, internship preparation, and competitive coding platforms that occasionally include system design rounds.

5. Self-Taught Programmers & Bootcamp Graduates: For self-learners who might have strong programming skills but limited exposure to architectural thinking, this MCQ set offers a guided, structured way to understand key concepts in system design without feeling overwhelmed.

6. Professionals Preparing for Certifications or Internal Promotions: If you’re targeting certifications (e.g., AWS Solutions Architect, Google Cloud Professional Architect) or internal promotions, this practice set helps reinforce the system thinking mindset needed for designing scalable solutions.

System Design Practice Set with Answers & Explanations

Role of System Designer (Single-select) – Concept-based

Q#1. Which of the following best describes the role of a system designer?

A) Managing the CI/CD pipeline and deployment scripts
B) Building low-level modules and APIs
C) Planning the system architecture to meet scalability and business needs
D) Conducting QA testing across environments

Answer: C

Explanation:

• A) Incorrect. CI/CD is the DevOps engineer’s role.
• B) Incorrect. This is more aligned with backend development.
• C) Correct. A system designer architects solutions to meet business and technical needs.
• D) Incorrect. QA testing is part of quality assurance, not design.

Importance of System Design (Multi-select) – Concept-based

Q#2. Which of the following are valid reasons why system design is important?

A) It helps in building scalable systems
B) It ensures better team collaboration
C) It prevents code duplication in local modules
D) It guides performance optimization at the architectural level

Answer: A, D

Explanation:

• A) Correct. Scalability is a core benefit of good system design.
• B) Incorrect. While system design may support collaboration, it is not its primary focus.
• C) Incorrect. Avoiding code duplication is a code-level concern, not a system design objective.
• D) Correct. System design allows for early architectural decisions that impact performance.

Definition of System Design (Single-select) – Concept-based

Q#3. What does System Design primarily focus on in the context of software systems?

A) Writing optimized algorithms for CPU-intensive tasks
B) Architecting scalable, maintainable, and reliable software systems
C) Structuring code within a single application
D) Managing agile team processes and sprint planning

Answer: B

Explanation:

• A) Incorrect. Optimized algorithms are more about low-level programming, not system design as a discipline.
• B) Correct. System design focuses on the architecture, scalability, maintainability, and reliability of the system.
• C) Incorrect. Code structuring is a software engineering concern, not full system design.
• D) Incorrect. This relates to project management, not system design.

Responsibilities of a System Designer (Multi-select) – Concept-based

Q#4. Which of the following are responsibilities of a system designer?

A) Defining the high-level architecture
B) Ensuring the system is horizontally scalable
C) Selecting UI theme and colors
D) Defining communication between microservices

Answer: A, B, D

Explanation:

• A) Correct. Defining architecture is a core responsibility.
• B) Correct. Scalability decisions are made at design time.
• C) Incorrect. UI themes are part of UI/UX design, not system design.
• D) Correct. Microservice interaction is a system-level concern.

Design Misconception (Single-select) – Concept-based

Q#5. Which of the following is a common misconception about system design?

A) It is critical for building scalable applications
B) It must always involve cloud-native solutions
C) It includes decisions on caching, databases, and APIs
D) It plays a role in handling system failures

Answer: B

Explanation:

• A) Incorrect. It is true that system design is critical for scalability.
• B) Correct. While cloud-native is common today, not all systems require it. On-premise and hybrid systems exist.
• C) Incorrect. These are valid components of system design.
• D) Incorrect. Handling failures is indeed a system design aspect.

Choosing Design Approach (Single-select) – Scenario-based

Q#6. You’re building a ride-sharing platform that will operate across multiple countries. What should be a system designer’s first priority?

A) Writing REST APIs for booking and ride assignment
B) Choosing a frontend framework for mobile app
C) Hiring drivers for each city
D) Designing a scalable and location-aware architecture

Answer: D

Explanation:

• A) Incorrect. This is a development task, not a system design priority.
• B) Incorrect. Frontend choice is important but not a system-level concern.
• C) Incorrect. Operational, not a system design issue
• D) Correct. The system must scale globally and manage geo-distributed logic, which is a core system design task.

Design Phases (Single-select) – Concept-based

Q#7. Which of the following typically comes first in the system design process?

A) Selecting database engine
B) Sketching the high-level system architecture
C) Writing service-level API contracts
D) Adding rate-limiting and retry mechanisms

Answer: B

Explanation:

• A) Incorrect. Database choice comes after understanding requirements and architecture.
• B) Correct. System design starts with high-level architecture diagrams.
• C) Incorrect. API contracts are detailed design steps.
• D) Incorrect. These are implementation-level details.

Early Design Mistake (Single-select) – Scenario-based

Q#8. A startup launched their app without a caching layer and is now facing slow page loads. What was the system design mistake here?

A) Failing to plan for scalability and response time
B) Ignoring network packet size
C) Choosing the wrong frontend framework
D) Not following TDD practices

Answer: A

Explanation:

• A) Correct. Not planning for caching, scalability, and performance is a system design failure.
• B) Incorrect. Network packet size optimization is advanced and unlikely the main cause.
• C) Incorrect. Frontend framework choice wouldn’t directly affect page speed from backend.
• D) Incorrect. TDD relates to testing, not design performance.

Design Trade-offs (Multi-select) – Scenario-based

Q#9. A video streaming platform wants to minimize video buffering without significantly increasing storage costs. What system design trade-offs might the team consider?

A) Using edge caching with CDNs
B) Increasing server CPU allocation
C) Reducing video resolution adaptively
D) Storing all videos in RAM

Answer: A, C

Explanation:

• A) Correct. CDNs reduce latency by caching near the user.
• B) Incorrect. CPU allocation does not directly address network-based buffering.
• C) Correct. Adaptive bitrate streaming reduces buffering by adjusting resolution.
• D) Incorrect. Storing all videos in RAM is not cost-effective or scalable.

System Designer’s Output (Single-select) – Concept-based

Q#10. What is a typical deliverable of a system designer?

A) Unit test cases
B) Database table indexes
C) JavaScript frontend validation logic
D) High-level architecture diagrams and component specifications

Answer: D

Explanation:

• A) Incorrect. Unit tests are written by developers.
• B) Incorrect. Indexes are part of database optimization.
• C) Incorrect. Frontend logic isn’t part of system design output.
• D) Correct. System designers deliver architecture diagrams, component roles, and interactions.

Missed Design Step (Single-select) – Scenario-based

Q#11. Your team scaled backend services horizontally but performance issues persist due to slow response times. What system design aspect was likely overlooked?

A) Client-side rendering
B) Caching strategy and database indexing
C) Rewriting API contracts
D) Upgrading CSS framework

Answer: B

Explanation:

• A) Incorrect. Client rendering won’t fix backend speed.
• B) Correct. Ignoring caching or indexing could still bottleneck even after horizontal scaling.
• C) Incorrect. API changes won’t improve core performance unless logic is optimized.
• D) Incorrect. CSS has no role in backend performance.

Responsibilities NOT Belonging to System Design (Multi-select) – Concept-based

Q#12. Which of the following are not typically considered part of a system designer’s responsibilities?

A) System availability planning
B) API gateway design
C) Unit test coverage reports
D) Selecting frontend component libraries

Answer: C, D

Explanation:

• A) Correct. Availability is a major design concern.
• B) Correct. Designing API Gateway interaction is in system design scope.
• C) Incorrect. Test reports are for QA/development.
• D) Incorrect. Frontend library selection is the frontend engineer’s task.

System Design Lifecycle (Single-select) – Concept-based

Q#13. At what stage of the software development lifecycle (SDLC) does system design usually occur?

A) After deployment
B) Before requirement gathering
C) Right after requirements analysis
D) After writing test cases

Answer: C

Explanation:

• A) Incorrect. System design is done much earlier.
• B) Incorrect. Requirements gathering must precede design.
• C) Correct. After requirements are known, design is the next logical step.
• D) Incorrect. Test cases come later in the SDLC.

 

Metrics Considered in System Design (Multi-select) – Concept-based

Q#14. Which of the following metrics are commonly considered during system design?

A) Latency
B) Load time of web pages
C) Scalability limits
D) Number of frontend DOM elements

Answer: A, C

Explanation:

• A) Correct. Latency impacts response time and user experience.
• B) Incorrect. Load time is frontend-focused.
• C) Correct. Scalability is a design priority.
• D) Incorrect. DOM elements relate to frontend/UI design.

Common Pitfall in System Design (Single-select) – Concept-based

Q#15. What is a common mistake developers make when skipping system design?

A) They write too many comments in code
B) They spend too much time optimizing queries
C) They create tightly coupled components
D) They forget to add CSS media queries

Answer: C

Explanation:

• A) Incorrect. Not a design-related issue.
• B) Incorrect. Optimizing queries is not a mistake unless it’s premature.
• C) Correct. Lack of upfront design can lead to tight coupling, harming maintainability.
• D) Incorrect. CSS responsiveness isn’t relevant here.

System Design Documents (Single-select) – Concept-based

Q#16. Which document would a system designer most likely produce?

A) Component diagram showing services and interactions
B) Wireframe for mobile UI layout
C) Gantt chart for sprint planning
D) Performance report from JMeter

Answer: A

Explanation:

• A) Correct. System design output includes component and interaction diagrams.
• B) Incorrect. Wireframes are a UI/UX artifact.
• C) Incorrect. Gantt charts are used in project management.
• D) Incorrect. JMeter is used for performance testing, not design.

High Availability Techniques (Multi-select) – Concept-based

Q#17. Which of the following design practices help improve system availability?

A) Load balancing
B) Single-point authentication service
C) Redundant server infrastructure
D) Scheduled downtime during traffic peaks

Answer: A, C

Explanation:

• A) Correct. Load balancing allows rerouting in case of node failure.
• B) Incorrect. Single points of failure reduce availability.
• C) Correct. Redundancy is key to availability.
• D) Incorrect. Downtime during peak traffic contradicts high availability.

Availability Issue (Single-select) – Scenario-based

Q#18. An e-commerce site crashes during a sale due to a failed payment gateway service. What availability flaw is evident here?

A) Lack of caching
B) Poor frontend optimization
C) Absence of fallback or redundancy
D) Incorrect database indexing

Answer: C

Explanation:

• A) Incorrect. Caching affects performance, not payment system availability.
• B) Incorrect. Frontend optimization doesn’t help if backend is down.
• C) Correct. Lack of redundancy or failover for critical services causes availability issues.
• D) Incorrect. Indexing is unrelated to system availability in this case.

Reliability Principles (Multi-select) – Concept-based

Q#19. Which features contribute to building a reliable system?

A) Retry mechanisms for transient failures
B) Monitoring and alerting systems
C) Hardcoding database credentials
D) Transactional integrity across microservices

Answer: A, B, D

Explanation:

• A) Correct. Retries help recover from temporary failures.
• B) Correct. Monitoring improves detection and reaction to issues.
• C) Incorrect. Hardcoding credentials introduces security and reliability risks.
• D) Correct. Transactional integrity ensures correct system state.

Performance Bottlenecks (Multi-select) – Concept-based

Q#20. Which components typically contribute to system performance bottlenecks?

A) Network latency
B) Poorly designed database queries
C) Redundant CSS classes
D) Inefficient load balancer configuration

Answer: A, B, D

Explanation:

• A) Correct. High latency increases response times.
• B) Correct. Slow queries degrade performance.
• C) Incorrect. CSS affects UI, not backend/system performance.
• D) Correct. Misconfigured load balancers can delay routing.

Handling Load Spikes (Single-select) – Scenario-based

Q#21. A ticket-booking system slows down dramatically during concert release events. What design solution could best help?

A) Replace frontend with React Native
B) Enable vertical scaling with better CPUs
C) Use message queues to decouple services during peak load
D) Disable user registration temporarily

Answer: C

Explanation:

• A) Incorrect. Frontend choice does not address system load.
• B) Incorrect. Vertical scaling helps to an extent, but not a long-term solution.
• C) Correct. Queues help absorb spikes, improving system resilience.
• D) Incorrect. Disabling features isn’t scalable or user-friendly.

Key Pillars of Secure Design (Multi-select) – Concept-based

Q#22. Which of the following are fundamental security principles in system design?

A) Data encryption at rest and in transit
B) Role-based access control (RBAC)
C) Hardcoded admin credentials
D) Input validation and sanitization

Answer: A, B, D

Explanation:

• A) Correct. Encryption protects data confidentiality.
• B) Correct. RBAC limits system access based on roles.
• C) Incorrect. Hardcoded credentials are a vulnerability.
• D) Correct. Input validation prevents injection attacks.

Maintainability Principles (Multi-select) – Concept-based

Q#23. Which of the following practices promote maintainability in system design?

A) Modular architecture
B) Tight coupling between components
C) Centralized logging
D) Clear interface contracts between services

Answer: A, C, D

Explanation:

• A) Correct. Modular systems are easier to maintain and test.
• B) Incorrect. Tight coupling makes code harder to update.
• C) Correct. Centralized logs assist in monitoring and debugging.
• D) Correct. Interface contracts help reduce integration issues.

Maintainability Mistake (Single-select) – Scenario-based

Q#24. An application has deeply nested code with shared global variables across services. Which principle is being violated?

A) Performance
B) Security
C) Maintainability
D) Availability

Answer: C

Explanation:

• A) Incorrect. Code structure does not directly impact performance.
• B) Incorrect. While globals can cause security risks, this case points to maintainability.
• C) Correct. Complex, interdependent code is hard to maintain.
• D) Incorrect. Availability refers to uptime and fault tolerance.

Scalability Considerations (Multi-select) – Concept-based

Q#25. Which design decisions are important when planning for scalability?

A) Stateless service design
B) Vertical scaling using SSDs
C) Shared-nothing architecture
D) Hardcoded database connections

Answer: A, C

Explanation:

• A) Correct. Stateless services can be replicated easily.
• B) Incorrect. SSDs help with speed but not scaling strategy.
• C) Correct. Shared-nothing architecture promotes distributed scaling.
• D) Incorrect. Hardcoding reduces flexibility and violates good design.

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