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LLDsystem_design~12 mins

Requirements and use cases in LLD - Architecture Diagram

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System Overview - Requirements and use cases

This system captures and manages requirements and use cases for software projects. It helps teams collect, organize, and track what the software must do and how users will interact with it. Key needs include clear documentation, easy updates, and traceability between requirements and use cases.

Architecture Diagram
User
  |
  v
Web Client
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +-------------------+
  |                   |
  v                   v
Requirements Service  Use Case Service
  |                   |
  v                   v
Database             Database
  |
  v
Cache
Components
User
actor
Interacts with the system to create and view requirements and use cases
Web Client
frontend
User interface for managing requirements and use cases
Load Balancer
load_balancer
Distributes incoming requests evenly to backend services
API Gateway
api_gateway
Routes requests to appropriate backend services and handles authentication
Requirements Service
service
Manages requirement data including creation, updates, and retrieval
Use Case Service
service
Manages use case data and links them to requirements
Database
database
Stores persistent data for requirements and use cases
Cache
cache
Speeds up frequent read operations for requirements and use cases
Request Flow - 13 Hops
User → Web Client
Web Client → Load Balancer
Load Balancer → API Gateway
API Gateway → Requirements Service
Requirements Service → Cache
Cache → Requirements Service
Requirements Service → Database
Database → Requirements Service
Requirements Service → Cache
Requirements Service → API Gateway
API Gateway → Load Balancer
Load Balancer → Web Client
Web Client → User
Failure Scenario
Component Fails:Database
Impact:New writes fail and fresh reads cannot be served; cached reads still work but may be stale
Mitigation:Use database replication for failover; rely on cache for read availability; alert admins for repair
Architecture Quiz - 3 Questions
Test your understanding
Which component routes user requests to the correct backend service?
ALoad Balancer
BAPI Gateway
CCache
DDatabase
Design Principle
This architecture separates concerns by using dedicated services for requirements and use cases, fronted by an API Gateway for routing and security. Caching improves read performance and reduces database load. Load balancing ensures even traffic distribution. The design supports scalability, fault tolerance, and clear data flow.