System design interview structure in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary goal of the initial requirements gathering phase in a system design interview?

During the first step of a system design interview, what is the main purpose of gathering requirements?

A To estimate the cost of the system implementation

B To immediately start drawing the architecture diagram

C To write code for the system components

D To understand the problem scope and clarify functional and non-functional requirements

💡 Hint

Think about what helps you know what to build before designing.

The initial phase focuses on understanding what the system should do and its constraints, which guides the design decisions.

❓ Architecture

intermediate

Which component is essential to handle high traffic in a scalable web system design?

In designing a web system that must handle millions of users, which component helps distribute user requests efficiently?

A Database index

B Load balancer

C Monolithic server

D Static HTML pages

💡 Hint

Think about how to spread work evenly across servers.

A load balancer distributes incoming traffic across multiple servers to prevent overload and improve availability.

❓ scaling

advanced

What is the main tradeoff when choosing between vertical and horizontal scaling?

When scaling a system, what is the key difference and tradeoff between adding more power to one server versus adding more servers?

A Vertical scaling requires rewriting code; horizontal scaling does not

B Vertical scaling is cheaper and unlimited; horizontal scaling is expensive and limited

C Vertical scaling increases power of one server but has limits; horizontal scaling adds servers and improves fault tolerance

D Vertical scaling improves network speed; horizontal scaling improves CPU speed

💡 Hint

Consider limits of hardware and benefits of multiple machines.

Vertical scaling boosts one machine's resources but hits hardware limits; horizontal scaling adds machines, improving capacity and fault tolerance.

❓ tradeoff

advanced

Which consistency model sacrifices immediate data accuracy for better availability in distributed systems?

In distributed system design, which consistency approach allows data to be temporarily out of sync to keep the system available?

A Eventual consistency

B Strong consistency

C Immediate consistency

D Strict serializability

💡 Hint

Think about systems that accept delays in data syncing to avoid downtime.

Eventual consistency allows temporary differences in data across nodes to maintain availability and partition tolerance.

❓ estimation

expert

Estimate the number of requests per second a system must handle if it serves 10 million users daily with an average of 5 requests per user.

Given 10 million users each making 5 requests per day, what is the approximate average number of requests per second the system should support?

A Approximately 578 requests per second

B Approximately 5000 requests per second

C Approximately 2000 requests per second

D Approximately 10000 requests per second

💡 Hint

Calculate total requests per day, then divide by seconds in a day (86400).

Total requests = 10,000,000 * 5 = 50,000,000 per day. Dividing by 86400 seconds gives about 578 requests per second.