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LLDsystem_design~12 mins

When to use which behavioral pattern in LLD - Architecture Diagram

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System Overview - When to use which behavioral pattern

This system helps developers decide which behavioral design pattern to use based on common software design problems. It guides users through scenarios like managing object communication, controlling algorithm variations, or handling state changes, recommending the best pattern for each case.

Architecture Diagram
User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Behavioral Pattern Selector Service
  |          |           |
  v          v           v
Strategy Service  Observer Service   State Service
  |          |           |
  v          v           v
Database Cache  Message Queue
Components
User
client
Developer or learner requesting pattern recommendations
Load Balancer
load_balancer
Distributes incoming requests evenly to API Gateway instances
API Gateway
api_gateway
Routes requests to the Behavioral Pattern Selector Service
Behavioral Pattern Selector Service
service
Analyzes user input and selects the appropriate behavioral pattern
Strategy Service
service
Handles requests related to the Strategy pattern use cases
Observer Service
service
Handles requests related to the Observer pattern use cases
State Service
service
Handles requests related to the State pattern use cases
Database
database
Stores pattern definitions, use cases, and user queries
Cache
cache
Caches frequent pattern recommendations for faster response
Message Queue
queue
Manages asynchronous processing of complex pattern analysis
Request Flow - 14 Hops
User → Load Balancer
Load Balancer → API Gateway
API Gateway → Cache
Cache → API Gateway
API Gateway → Behavioral Pattern Selector Service
Behavioral Pattern Selector Service → Strategy Service
Behavioral Pattern Selector Service → Observer Service
Behavioral Pattern Selector Service → State Service
Behavioral Pattern Selector Service → Database
Database → Behavioral Pattern Selector Service
Behavioral Pattern Selector Service → Cache
Behavioral Pattern Selector Service → API Gateway
API Gateway → Load Balancer
Load Balancer → User
Failure Scenario
Component Fails:Database
Impact:Cached recommendations still work but new queries fail
Mitigation:System continues working by serving from cache; implement failover or circuit breaker
Architecture Quiz - 3 Questions
Test your understanding
Which component first checks if a pattern recommendation is already available to speed up response?
AAPI Gateway
BCache
CDatabase
DLoad Balancer
Design Principle
This architecture demonstrates modular design by separating concerns into specialized services for each behavioral pattern. It uses caching to improve performance and a load balancer with API gateway to manage traffic efficiently. Delegation to pattern-specific services allows scalability and easier maintenance.