What LLD covers vs HLD - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Difference between LLD and HLD focus areas

Which of the following best describes the primary focus of Low-Level Design (LLD) compared to High-Level Design (HLD)?

A LLD focuses on user interface design; HLD focuses on network protocols

B LLD defines system architecture and components; HLD specifies database schemas

C LLD details module internals and algorithms; HLD outlines system architecture and components

D LLD describes business goals; HLD describes coding standards

💡 Hint

Think about which design level zooms into the details inside modules.

LLD breaks down system components into detailed modules and algorithms, while HLD provides an overview of system architecture and major components.

❓ Architecture

intermediate

Components described in HLD vs LLD

Which components are typically described in High-Level Design but not in Low-Level Design?

A System modules and their interactions

B Class diagrams and method implementations

C Database table structures and indexes

D Detailed API request and response formats

💡 Hint

Consider which design level shows the big picture of the system.

HLD shows system modules and their interactions, while LLD focuses on internal details like classes and methods.

❓ scaling

advanced

How LLD supports scalability compared to HLD

In what way does Low-Level Design (LLD) contribute to system scalability differently than High-Level Design (HLD)?

A LLD creates deployment diagrams; HLD creates class diagrams

B LLD optimizes algorithms and data structures; HLD plans distributed system components

C LLD manages user roles; HLD manages database replication

D LLD defines network topology; HLD writes code for caching

💡 Hint

Think about how detailed design affects performance inside modules.

LLD focuses on optimizing algorithms and data structures for performance, while HLD plans system distribution and component scaling.

❓ tradeoff

advanced

Tradeoffs between LLD and HLD detail levels

What is a key tradeoff when choosing the level of detail between High-Level Design (HLD) and Low-Level Design (LLD)?

A HLD is only for small projects; LLD is only for large projects

B HLD requires coding skills; LLD requires business analysis

C HLD focuses on UI design; LLD focuses on database tuning

D HLD is faster to create but less precise; LLD is detailed but time-consuming

💡 Hint

Consider the effort and precision involved in each design level.

HLD provides a broad overview quickly but lacks detail; LLD provides detailed design but takes more time and effort.

❓ estimation

expert

Estimating effort for LLD vs HLD in a large system

You are tasked with designing a large, complex system. Which statement best estimates the relative effort required for Low-Level Design (LLD) compared to High-Level Design (HLD)?

A LLD requires significantly more effort than HLD due to detailed module design

B LLD and HLD require equal effort since both cover the entire system

C LLD requires less effort than HLD because it reuses existing components

D LLD requires no effort if HLD is well done

💡 Hint

Think about the depth of detail and documentation needed for each design level.

LLD involves detailed design of each module, which is more time-consuming than the broader HLD.

Practice

1. Which of the following best describes what High-Level Design (HLD) focuses on?

easy

A. Database schema and indexing details

B. Detailed class structures and method implementations

C. Writing code for individual modules

D. The overall system architecture and main components

Solution

1. Step 1: Understand HLD purpose

   HLD is about the big picture, showing main parts and how they connect.

2. Step 2: Compare options

   Only The overall system architecture and main components describes overall architecture and main components, which matches HLD.

3. Final Answer:

   The overall system architecture and main components -> Option D

4. Quick Check:

   HLD = overall system view [OK]

Hint: HLD = big picture, LLD = details [OK]

Common Mistakes:

• Confusing HLD with detailed coding
• Thinking HLD includes method-level details
• Mixing database design with HLD focus

2. Which of these is typically included in Low-Level Design (LLD)?

easy

A. System component interactions

B. User interface wireframes

C. Class diagrams with methods and attributes

D. Network topology diagrams

Solution

1. Step 1: Identify LLD details

   LLD focuses on detailed design like classes, methods, and data structures.

2. Step 2: Match options to LLD

   Class diagrams with methods and attributes describes class diagrams with methods and attributes, which fits LLD.

3. Final Answer:

   Class diagrams with methods and attributes -> Option C

4. Quick Check:

   LLD = detailed class design [OK]

Hint: LLD = classes and methods details [OK]

Common Mistakes:

• Choosing high-level diagrams for LLD
• Confusing UI design with LLD
• Mixing network diagrams with LLD

3. Given a system design process, which step correctly uses HLD and LLD?

medium

A. Write detailed code first, then create HLD diagrams

B. Create HLD diagrams to plan architecture, then LLD for coding details

C. Skip HLD and directly write LLD documents

D. Use LLD to explain user requirements

Solution

1. Step 1: Understand design flow

   Good practice is to start with HLD for overall planning, then LLD for detailed design.

2. Step 2: Evaluate options

   Create HLD diagrams to plan architecture, then LLD for coding details matches this flow: HLD first, then LLD for coding guidance.

3. Final Answer:

   Create HLD diagrams to plan architecture, then LLD for coding details -> Option B

4. Quick Check:

   Design flow = HLD then LLD [OK]

Hint: Plan big picture first (HLD), then details (LLD) [OK]

Common Mistakes:

• Starting with code before design
• Skipping HLD and losing overview
• Using LLD for user requirements

4. A developer wrote detailed class diagrams but missed showing system modules and their interactions. What design level is missing?

medium

A. High-Level Design (HLD)

B. Low-Level Design (LLD)

C. Both HLD and LLD

D. Neither HLD nor LLD

Solution

1. Step 1: Analyze given design

   Detailed class diagrams are part of LLD, but system modules and interactions belong to HLD.

2. Step 2: Identify missing design level

   Since modules and their interactions are missing, HLD is incomplete.

3. Final Answer:

   High-Level Design (HLD) -> Option A

4. Quick Check:

   Missing modules = missing HLD [OK]

Hint: Modules and interactions belong to HLD [OK]

Common Mistakes:

• Confusing class diagrams with HLD
• Thinking LLD covers system modules
• Assuming both designs are missing

5. You are designing a new feature for a large system. Which approach correctly uses HLD and LLD to ensure scalability and maintainability?

hard

A. Design the system modules and their interactions first, then define classes and methods

B. Focus only on database schema and skip other designs

C. Write code immediately and document design later

D. Start with detailed class design, then create overall system diagrams

Solution

1. Step 1: Understand scalable design approach

   Good design starts with HLD to define modules and interactions, then LLD for detailed classes.

2. Step 2: Evaluate options for best practice

   Design the system modules and their interactions first, then define classes and methods follows this approach, ensuring clear structure and maintainability.

3. Final Answer:

   Design the system modules and their interactions first, then define classes and methods -> Option A

4. Quick Check:

   HLD first, then LLD for scalable design [OK]

Hint: Big picture first, then details for scalable design [OK]

Common Mistakes:

• Starting with code before design
• Ignoring system modules and interactions
• Focusing only on database schema