What high level design encompasses in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Key components of High Level Design

Which of the following best describes what High Level Design (HLD) includes?

A Unit test cases and code-level logic

B Overall system architecture, major components, and their interactions

C Detailed database schema and exact API endpoints

D User interface pixel-perfect design and color schemes

💡 Hint

Think about the big picture view of the system rather than detailed parts.

High Level Design focuses on the overall system structure, major modules, and how they communicate. It does not go into detailed code or UI specifics.

❓ Architecture

intermediate

Identifying High Level Design elements in a system

Which of the following is NOT typically part of High Level Design?

A Specifying exact class methods and variables

B Describing data flow between components

C Defining system modules and their responsibilities

D Choosing technology stack and protocols

💡 Hint

Consider what level of detail HLD usually avoids.

HLD does not specify exact class methods or variables; that is part of Low Level Design (LLD).

❓ scaling

advanced

High Level Design considerations for scalability

When creating a High Level Design for a scalable web application, which design aspect is most important to include?

A Exact UI element positioning for mobile devices

B Detailed SQL query optimization techniques

C Load balancing and distributed system components

D Specific error handling code snippets

💡 Hint

Think about how the system handles many users and traffic.

Load balancing and distributed components are key to scalability and are part of High Level Design.

❓ tradeoff

advanced

Tradeoffs in High Level Design decisions

Which tradeoff is commonly considered during High Level Design?

A Deciding exact variable names for code clarity

B Writing unit tests for each function

C Selecting font sizes for user readability

D Choosing between synchronous and asynchronous communication for system modules

💡 Hint

Focus on communication patterns between components.

High Level Design involves decisions like synchronous vs asynchronous communication which affect performance and complexity.

❓ estimation

expert

Estimating capacity in High Level Design

You are designing a High Level Design for a video streaming service expecting 10 million daily users. Which capacity estimate is most relevant at this stage?

A Number of servers needed to handle peak concurrent streams

B Exact database schema for user profiles

C Detailed UI wireframes for video player controls

D Specific error messages for playback failures

💡 Hint

Consider what affects system capacity and performance at a high level.

Estimating the number of servers for peak load is a critical capacity planning aspect in High Level Design.

Practice

1. What does a high level design (HLD) primarily show in a system?

easy

A. The user interface colors and fonts

B. The main components and how they connect

C. The detailed database schema

D. The exact code for each module

Solution

1. Step 1: Understand the purpose of HLD

   HLD focuses on the big picture, showing main parts and their relationships.

2. Step 2: Differentiate from detailed design

   Detailed code or UI specifics are not part of HLD but come later in design phases.

3. Final Answer:

   The main components and how they connect -> Option B

4. Quick Check:

   HLD = Big parts and connections [OK]

Hint: HLD = big parts + connections, not code or UI [OK]

Common Mistakes:

• Confusing HLD with detailed design
• Thinking HLD includes UI styling
• Assuming HLD shows exact code

2. Which of the following is a correct element to include in a high level design document?

easy

A. Component diagrams showing system parts

B. Detailed API code snippets

C. Exact SQL queries for database

D. Pixel-perfect UI mockups

Solution

1. Step 1: Identify typical HLD contents

   HLD includes diagrams of components and their interactions, not code or UI details.

2. Step 2: Eliminate incorrect options

   Code snippets, SQL queries, and UI mockups belong to detailed design or implementation.

3. Final Answer:

   Component diagrams showing system parts -> Option A

4. Quick Check:

   HLD = component diagrams [OK]

Hint: HLD shows diagrams, not code or UI details [OK]

Common Mistakes:

• Including code snippets in HLD
• Confusing HLD with low-level design
• Adding UI mockups in HLD

3. Given a high level design showing components A, B, and C connected in sequence, what is the most likely data flow?

medium

A. Data flows from A to B to C

B. Data flows from C to B to A

C. Data flows randomly between components

D. No data flows between components

Solution

1. Step 1: Analyze component connections

   Sequence connection means data moves in order from first to last component.

2. Step 2: Determine flow direction

   Data flows from A to B to C as per the sequence shown.

3. Final Answer:

   Data flows from A to B to C -> Option A

4. Quick Check:

   Sequence = A -> B -> C data flow [OK]

Hint: Follow arrows in sequence for data flow direction [OK]

Common Mistakes:

• Reversing data flow direction
• Assuming random data flow
• Ignoring component connections

4. A high level design diagram shows a database connected directly to the user interface without any backend service. What is the main issue here?

medium

A. Database should connect only to frontend

B. Too many components included

C. Missing backend layer to handle business logic

D. User interface should connect directly to database

Solution

1. Step 1: Identify missing architectural layer

   Backend services handle logic and security between UI and database.

2. Step 2: Understand why direct UI to database is bad

   Direct connection risks security and breaks separation of concerns.

3. Final Answer:

   Missing backend layer to handle business logic -> Option C

4. Quick Check:

   Backend needed between UI and database [OK]

Hint: UI never connects directly to database [OK]

Common Mistakes:

• Thinking UI can safely connect to database
• Ignoring backend role
• Confusing component count with design quality

5. When creating a high level design for a scalable web application, which of the following should be included?

hard

A. Detailed SQL queries for data retrieval

B. Exact CSS styles for responsive design

C. User passwords and encryption keys

D. Components like load balancers, web servers, and databases with their interactions

Solution

1. Step 1: Identify scalable system components

   Load balancers, web servers, and databases are key parts for scalability.

2. Step 2: Exclude irrelevant details

   CSS styles, SQL queries, and sensitive data are not part of HLD.

3. Final Answer:

   Components like load balancers, web servers, and databases with their interactions -> Option D

4. Quick Check:

   HLD = scalable components + interactions [OK]

Hint: Include scalable components, exclude code and secrets [OK]

Common Mistakes:

• Adding UI styles in HLD
• Including sensitive data in design
• Confusing HLD with implementation details