Requirements and use cases in LLD - System Design Exercise

Design: Requirements and Use Cases Analysis

Focus on gathering and analyzing requirements and use cases for a new system. Out of scope are detailed system architecture and implementation.

Functional Requirements

FR1: Identify and document functional requirements clearly

FR2: Capture non-functional requirements such as performance, scalability, and availability

FR3: Define user roles and their interactions with the system

FR4: Create use cases that describe how users achieve goals with the system

FR5: Ensure requirements are testable and measurable

Non-Functional Requirements

NFR1: Requirements must be realistic and achievable within project scope

NFR2: Use cases should be simple and understandable by non-technical stakeholders

NFR3: Requirements must support scalability to handle up to 10,000 concurrent users

NFR4: Latency targets for key operations should be under 200ms

NFR5: Availability target is 99.9% uptime

Think Before You Design

Questions to Ask

❓ Question 1

❓ Question 2

❓ Question 3

❓ Question 4

❓ Question 5

Key Components

User personas and roles

Functional requirement lists

Non-functional requirement definitions

Use case diagrams or narratives

Requirement traceability matrix

Design Patterns

User story mapping

Use case modeling

Requirement prioritization (MoSCoW)

Acceptance criteria definition

Stakeholder interviews and workshops

Reference Architecture

  +-------------------+
  |   Stakeholders    |
  +---------+---------+
            |
            v
  +-------------------+
  | Requirements Team |
  +---------+---------+
            |
            v
  +-------------------+
  | Use Case Analysis |
  +---------+---------+
            |
            v
  +-------------------+
  | Requirement Docs  |
  +-------------------+

Components

Stakeholders

Interviews, Workshops

Provide input on needs and goals

Requirements Team

Requirement Management Tools (e.g., Jira, Confluence)

Gather, document, and validate requirements

Use Case Analysis

Use Case Diagrams, User Stories

Define user interactions and system behavior

Requirement Documents

Text Documents, Spreadsheets

Store and communicate requirements and use cases

Request Flow

1. Stakeholders provide input on needs and goals

2. Requirements team collects and documents functional and non-functional requirements

3. Use case analysts create use cases describing user interactions

4. Requirements and use cases are reviewed and validated with stakeholders

5. Final documents are stored and used for system design and development

Database Schema

Entities: - Stakeholder(id, name, role, contact_info) - Requirement(id, type [functional/non-functional], description, priority, status) - UseCase(id, title, description, actor_id, preconditions, postconditions) Relationships: - Stakeholder to Requirement: 1:N (a stakeholder can provide many requirements) - UseCase to Stakeholder: N:1 (each use case involves one primary actor/stakeholder)

Scaling Discussion

Bottlenecks

Difficulty managing large numbers of requirements and use cases as system grows

Ensuring all stakeholder inputs are captured and conflicts resolved

Maintaining traceability between requirements and use cases

Keeping documentation up to date with changing requirements

Solutions

Use specialized requirement management tools with filtering and tagging

Establish clear communication channels and regular review meetings

Implement traceability matrices linking requirements to use cases and tests

Adopt agile practices for continuous requirement refinement and validation

Interview Tips

Time: Spend 10 minutes understanding the problem and clarifying requirements, 15 minutes discussing use case creation and documentation, 10 minutes on challenges and scaling, and 10 minutes on summarizing and answering questions.

Importance of clear, testable requirements

Role of use cases in understanding user interactions

Balancing functional and non-functional requirements

Handling conflicting stakeholder needs

Maintaining documentation and traceability