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LLDsystem_design~12 mins

Simplify debts algorithm in LLD - Architecture Diagram

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System Overview - Simplify debts algorithm

This system helps a group of people settle debts among themselves with the fewest transactions possible. It calculates who owes whom and how much, then suggests simplified payments to clear all debts efficiently.

Architecture Diagram
User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Debt Simplification Service
  |
  +------------------+
  |                  |
  v                  v
Database           Cache
Components
User
client
Initiates debt data input and requests simplified debt results
Load Balancer
load_balancer
Distributes incoming user requests evenly to API Gateway instances
API Gateway
api_gateway
Handles authentication, routing, and request validation before forwarding to service
Debt Simplification Service
service
Processes debts data, runs the simplify debts algorithm, and returns optimized transactions
Database
database
Stores user debts data and transaction history
Cache
cache
Stores recent simplified debt results for quick retrieval to reduce computation
Request Flow - 9 Hops
User → Load Balancer
Load Balancer → API Gateway
API Gateway → Cache
Cache → API Gateway
API Gateway → Debt Simplification Service
Debt Simplification Service → Database
Debt Simplification Service → Cache
Debt Simplification Service → API Gateway
API Gateway → User
Failure Scenario
Component Fails:Database
Impact:New debts cannot be saved or updated; service cannot fetch latest debts data, causing stale or failed responses
Mitigation:Use database replication for failover; serve cached results if available; notify users of degraded service
Architecture Quiz - 3 Questions
Test your understanding
Which component first checks if the simplified debts result is already available to avoid recomputation?
ALoad Balancer
BDatabase
CCache
DDebt Simplification Service
Design Principle
This architecture uses caching to reduce repeated computation and database load, a load balancer to distribute user requests, and a dedicated service to run the simplify debts algorithm. It ensures scalability and responsiveness by separating concerns and using fast cache lookups before expensive computations.