Requirements gathering (functional and non-functional) in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identify the correct functional requirement

Which of the following is a functional requirement for an online bookstore system?

A The system shall allow users to search for books by title, author, or ISBN.

B The system shall be available 99.9% of the time.

C The system shall respond to user requests within 2 seconds.

D The system shall encrypt user passwords using AES-256.

💡 Hint

Functional requirements describe what the system should do.

Option A describes a specific feature the system must provide, which is a functional requirement. Options A, B, and D describe qualities or constraints, which are non-functional requirements.

🧠 Conceptual

intermediate

Identify the non-functional requirement

Which of the following is a non-functional requirement for a mobile banking app?

A The app shall allow users to transfer money to other accounts.

B The app shall support fingerprint authentication for login.

C The app shall process transactions within 3 seconds.

D The app shall provide monthly account statements.

💡 Hint

Non-functional requirements describe how the system performs or behaves.

Option C specifies a performance constraint (processing time), which is a non-functional requirement. Options B, C, and D describe features or functions.

❓ tradeoff

advanced

Tradeoff between functional and non-functional requirements

A video streaming service wants to add a new feature to allow offline downloads (functional requirement). However, this feature may increase storage costs and affect app performance (non-functional concerns). What is the best approach to handle this tradeoff?

A Remove the feature to keep non-functional requirements intact.

B Analyze impact, optimize feature design, and balance both requirements.

C Delay the feature indefinitely until non-functional issues disappear.

D Ignore non-functional concerns and implement the feature fully.

💡 Hint

Good system design balances functional and non-functional needs.

Option B suggests analyzing and optimizing to balance both types of requirements, which is best practice. Options A and B are extreme and ignore important concerns. Option B delays progress unnecessarily.

❓ Architecture

advanced

Classify requirements for a ride-sharing app

Given these requirements for a ride-sharing app, classify each as functional (F) or non-functional (NF):
1. The app shall allow users to book rides.
2. The app shall encrypt user data.
3. The app shall handle 10,000 concurrent users.
4. The app shall provide driver ratings.

A 1-F, 2-NF, 3-NF, 4-F

B 1-F, 2-F, 3-NF, 4-NF

C 1-NF, 2-F, 3-F, 4-NF

D 1-NF, 2-NF, 3-F, 4-F

💡 Hint

Functional requirements describe features; non-functional describe qualities.

Booking rides and driver ratings are features (functional). Encrypting data and handling many users are qualities (non-functional).

❓ estimation

expert

Estimate capacity based on non-functional requirements

A new messaging app expects 1 million daily active users. The non-functional requirement states the system must handle peak loads with 10 messages per user per day, with 99.99% uptime. What is the minimum message processing capacity per second the system should support during peak hours (assuming peak hour is 10% of the day)?

A Approximately 1,000,000 messages per second

B Approximately 1,157,400 messages per second

C Approximately 11,574 messages per second

D Approximately 1,157 messages per second

💡 Hint

Calculate total messages per day, then divide by peak hour seconds.

Total messages = 1,000,000 users * 10 messages = 10,000,000 messages/day.
Peak hour = 10% of 24 hours = 2.4 hours = 8640 seconds.
Capacity = 10,000,000 / 8640 ≈ 1157 messages/sec.
Check options carefully; option D matches closest after unit conversion.