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Microservicessystem_design~12 mins

Correlation IDs in Microservices - Architecture Diagram

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System Overview - Correlation IDs

This system demonstrates how correlation IDs help track requests across multiple microservices. Each incoming user request gets a unique ID that travels through services, making debugging and monitoring easier.

Architecture Diagram
User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Service A <--> Service B
  |           |
  v           v
Database     Cache
Components
User
client
Initiates requests to the system
Load Balancer
load_balancer
Distributes incoming requests evenly to API Gateway instances
API Gateway
api_gateway
Receives requests, assigns correlation IDs, and routes to services
Service A
service
Handles main business logic and calls downstream services
Service B
service
Performs auxiliary tasks and caching
Database
database
Stores persistent data for services
Cache
cache
Speeds up data retrieval for Service B
Request Flow - 10 Hops
User → Load Balancer
Load Balancer → API Gateway
API Gateway → Service A
Service A → Service B
Service B → Cache
Service B → Database
Service B → Service A
Service A → API Gateway
API Gateway → Load Balancer
Load Balancer → User
Failure Scenario
Component Fails:API Gateway
Impact:New requests cannot be assigned correlation IDs or routed, causing request failures and loss of traceability.
Mitigation:Use multiple API Gateway instances with health checks and automatic failover to maintain availability and correlation ID assignment.
Architecture Quiz - 3 Questions
Test your understanding
Where is the correlation ID first assigned in the request flow?
AAt the Load Balancer
BAt Service A
CAt the API Gateway
DAt the Database
Design Principle
Assigning a unique correlation ID at the API Gateway and passing it through all services enables end-to-end request tracking. This helps debugging and monitoring in complex microservice systems.