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HLDsystem_design~12 mins

Order processing pipeline in HLD - Architecture Diagram

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System Overview - Order processing pipeline

This system handles customer orders from submission to completion. It ensures orders are received, validated, processed, and stored reliably while providing quick responses and handling failures gracefully.

Architecture Diagram
User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Order Service ---> Cache
  |
  v
Message Queue ---> Inventory Service
  |
  v
Database
Components
User
client
Initiates order requests
Load Balancer
load_balancer
Distributes incoming requests evenly to API Gateway instances
API Gateway
api_gateway
Receives requests, handles authentication and routing to Order Service
Order Service
service
Validates and processes orders, interacts with cache and message queue
Cache
cache
Stores recent order data for quick access
Message Queue
queue
Queues order processing tasks asynchronously for Inventory Service
Inventory Service
service
Updates inventory based on orders from the queue
Database
database
Stores all order and inventory data persistently
Request Flow - 10 Hops
User → Load Balancer
Load Balancer → API Gateway
API Gateway → Order Service
Order Service → Cache
Order Service → Message Queue
Message Queue → Inventory Service
Inventory Service → Database
Order Service → Database
Order Service → API Gateway
API Gateway → User
Failure Scenario
Component Fails:Database
Impact:Order data cannot be saved; inventory updates fail; system may lose data consistency
Mitigation:Reads can still be served from cache; writes are retried; database replication and failover ensure availability
Architecture Quiz - 3 Questions
Test your understanding
Which component handles distributing incoming user requests to prevent overload?
AMessage Queue
BAPI Gateway
CLoad Balancer
DCache
Design Principle
This design uses asynchronous processing with a message queue to decouple order submission from inventory updates, improving scalability and reliability. Caching reduces database load and speeds up responses. Load balancing and API gateway ensure even traffic distribution and security.