What high level design encompasses in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of High Level Design (HLD)?

HLD provides a big picture view of the system, showing how components interact and the overall architecture without going into detailed coding or implementation.

beginner

Name three key components typically included in a High Level Design document.

1. System architecture diagram
2. Module/component descriptions
3. Data flow and interaction between components

intermediate

How does High Level Design differ from Low Level Design?

HLD focuses on the overall system structure and relationships between modules, while Low Level Design details the internal logic, algorithms, and data structures within each module.

intermediate

Why is scalability considered in High Level Design?

Because HLD plans how the system can grow and handle more users or data by designing flexible components and choosing appropriate technologies early on.

beginner

What role do external interfaces play in High Level Design?

They define how the system communicates with other systems or users, specifying APIs, protocols, and data formats at a high level.

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

A Module interaction overview

B Detailed code logic

C System architecture diagram

D Technology stack selection

Detailed code logic is part of Low Level Design, not High Level Design.

What does High Level Design primarily focus on?

A Database indexing

B Detailed algorithms

C Unit testing

D Overall system structure

HLD focuses on the overall system structure and component relationships.

Which document would you expect to find a data flow diagram in?

A High Level Design

B Low Level Design

C Test Plan

D User Manual

Data flow diagrams showing component interactions are part of High Level Design.

Why is technology stack selection important in High Level Design?

A It is used for writing unit tests

B It defines variable names

C It affects system scalability and maintainability

D It determines user interface colors

Choosing the right technology stack impacts how well the system can grow and be maintained.

Which of these is a key output of High Level Design?

A System architecture diagram

B Debug logs

C Code comments

D Class method implementations

System architecture diagrams are a key output of High Level Design.

Explain what High Level Design encompasses and why it is important in system development.

Think about how HLD helps teams understand the system before coding.

Describe the difference between High Level Design and Low Level Design with examples.

Compare the scope and detail level of each design phase.

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