System Overview - Fine calculation
This system calculates fines for users based on predefined rules such as late returns or violations. It must handle multiple fine types, apply correct rates, and provide results quickly and accurately.
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Fine calculation in LLD - Architecture Diagram
Architecture Diagram
User | v Load Balancer | v API Gateway | v Fine Calculation Service | | v v Cache Database | | v v Response Fine Rules Storage
Components
User
user
Initiates fine calculation requests
Load Balancer
load_balancer
Distributes incoming requests evenly to services
API Gateway
api_gateway
Handles request routing, authentication, and rate limiting
Fine Calculation Service
service
Processes fine calculation logic using rules and user data
Cache
cache
Stores recent fine calculation results for quick retrieval
Database
database
Stores user data and fine calculation history
Fine Rules Storage
database
Stores fine calculation rules and rates
Response
response
Delivers fine calculation results back to the user
Request Flow - 11 Hops
User → Load Balancer
Load Balancer → API Gateway
API Gateway → Fine Calculation Service
Fine Calculation Service → Cache
Cache → Fine Calculation Service
Fine Calculation Service → Database
Fine Calculation Service → Fine Rules Storage
Fine Calculation Service → Cache
Fine Calculation Service → API Gateway
API Gateway → Load Balancer
Load Balancer → User
Failure Scenario
Component Fails:Cache
Impact:Fine Calculation Service must query database for every request, increasing latency
Mitigation:System continues working by fetching data from database; cache can be restored or replaced without downtime
Architecture Quiz - 3 Questions
Test your understanding
Which component first handles the user's fine calculation request?
Design Principle
This architecture uses caching to reduce database load and improve response times. It separates concerns by isolating fine rules in a dedicated storage and uses an API Gateway for security and routing. Load balancing ensures scalability and availability.