Why Requirements analysis in LLD? - Purpose & Use Cases

The Big Idea

What if you could avoid costly rework by simply asking the right questions first?

The Scenario

Imagine building a house without a clear plan. You start laying bricks, but halfway through, you realize the rooms are too small or the doors don't fit. You have to tear down walls and redo work, wasting time and money.

The Problem

Without proper requirements analysis, projects become confusing and chaotic. Teams guess what users want, leading to mistakes, delays, and frustration. Fixing problems late is costly and stressful.

The Solution

Requirements analysis acts like a blueprint for your project. It helps gather clear, detailed needs from users before building. This way, everyone agrees on what to build, reducing errors and saving time.

Before vs After

✗ Before

Build features based on assumptions
Fix bugs after release

✓ After

Gather user needs first
Design system to meet those needs

What It Enables

Clear requirements enable smooth project flow and deliver exactly what users want.

Real Life Example

Before launching a new app, a team interviews users to understand their problems. They document these needs clearly, so the app solves real issues from day one.

Key Takeaways

Requirements analysis prevents costly mistakes by clarifying needs early.

It aligns teams and users on project goals.

It saves time and resources by guiding focused development.

Practice

1. What is the main purpose of requirements analysis in system design?

easy

A. To deploy the system to users

B. To write the system code

C. To test the system performance

D. To define what the system must do

Solution

1. Step 1: Understand the role of requirements analysis

   Requirements analysis focuses on understanding and defining the system's needs and functions.

2. Step 2: Differentiate from other phases

   Writing code, testing, and deployment happen after requirements are clear.

3. Final Answer:

   To define what the system must do -> Option D

4. Quick Check:

   Requirements analysis = Define system needs [OK]

Hint: Requirements analysis = What system must do [OK]

Common Mistakes:

• Confusing requirements analysis with coding
• Thinking testing is part of requirements
• Mixing deployment with requirements gathering

2. Which of the following is a correct step in requirements analysis?

easy

A. Writing deployment scripts

B. Compiling source code

C. Gathering user needs

D. Running system tests

Solution

1. Step 1: Identify key activities in requirements analysis

   Gathering user needs is essential to understand what the system should do.

2. Step 2: Exclude unrelated activities

   Deployment scripts, compiling code, and testing happen after requirements are set.

3. Final Answer:

   Gathering user needs -> Option C

4. Quick Check:

   Requirements analysis = Gather needs [OK]

Hint: Gather user needs first in requirements analysis [OK]

Common Mistakes:

• Mixing coding or deployment with requirements
• Ignoring user input during analysis
• Confusing testing with requirements gathering

3. Given these requirements:
- System must handle 1000 users simultaneously
- Data must be encrypted
- Users can reset passwords
Which requirement type is "Data must be encrypted"?

medium

A. Non-functional requirement

B. Functional requirement

C. Business requirement

D. User interface requirement

Solution

1. Step 1: Classify the requirement "Data must be encrypted"

   This describes a quality or constraint on the system, not a specific function.

2. Step 2: Understand requirement types

   Functional requirements describe actions; non-functional describe qualities like security.

3. Final Answer:

   Non-functional requirement -> Option A

4. Quick Check:

   Encryption = Non-functional requirement [OK]

Hint: Security needs are non-functional requirements [OK]

Common Mistakes:

• Confusing security with functional features
• Mixing business goals with technical details
• Assuming all requirements are functional

4. A requirements document states: "Users must login with username and password." Later, it says: "Users can login using email and password." What is the main issue here?

medium

A. Performance bottleneck

B. Ambiguous requirements

C. Security vulnerability

D. Scalability problem

Solution

1. Step 1: Identify conflicting statements

   The document gives two different login methods without clarifying which is correct.

2. Step 2: Understand impact of ambiguity

   Ambiguous requirements confuse developers and cause design errors.

3. Final Answer:

   Ambiguous requirements -> Option B

4. Quick Check:

   Conflicting login info = Ambiguity [OK]

Hint: Conflicting info means ambiguous requirements [OK]

Common Mistakes:

• Assuming security or performance issues without evidence
• Ignoring requirement conflicts
• Thinking scalability relates to login methods

5. You are designing a messaging app. Which of these is the best way to gather requirements to ensure scalability and user satisfaction?

hard

A. Interview users, analyze competitors, and document clear functional and non-functional needs

B. Start coding immediately based on your assumptions

C. Only focus on UI design without backend planning

D. Ignore user feedback and add features later

Solution

1. Step 1: Identify best practices in requirements gathering

   Interviewing users and analyzing competitors helps understand real needs and market standards.

2. Step 2: Emphasize clear documentation of all requirements

   Clear functional and non-functional requirements guide scalable and user-friendly design.

3. Final Answer:

   Interview users, analyze competitors, and document clear functional and non-functional needs -> Option A

4. Quick Check:

   User research + clear docs = good requirements [OK]

Hint: Gather user input and document clearly before coding [OK]

Common Mistakes:

• Skipping user research
• Starting development without clear requirements
• Ignoring backend needs for scalability