HLDsystem_design~12 mins

Message ordering guarantees in HLD - Architecture Diagram

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System Overview - Message ordering guarantees

This system ensures that messages sent between services are received and processed in the exact order they were sent. It is crucial for applications like chat systems, financial transactions, or event processing where the sequence of messages affects correctness.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Message Producer Service
  |
  v
Message Queue (Partitioned with Ordering)
  |
  v
Message Consumer Service
  |
  v
Database
  |
  v
Cache

Components

User

client

Initiates message sending requests

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Handles client requests and routes them to the producer service

Message Producer Service

service

Accepts messages from clients and publishes them to the message queue with ordering keys

Message Queue (Partitioned with Ordering)

message_queue

Stores messages in partitions that preserve order per key, ensuring ordered delivery

Message Consumer Service

service

Consumes messages from the queue in order and processes them, updating the database

Database

database

Stores processed message data persistently

Cache

cache

Provides fast access to frequently requested data

Request Flow - 9 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Message Producer Service

Message Producer Service → Message Queue (Partitioned with Ordering)

Message Queue (Partitioned with Ordering) → Message Consumer Service

Message Consumer Service → Database

Message Consumer Service → Cache

Message Consumer Service → API Gateway

API Gateway → User

Failure Scenario

Component Fails:Message Queue (Partitioned with Ordering)

Impact:Messages cannot be enqueued or dequeued, causing message loss or processing delays. Ordering guarantees are broken if failover is not handled properly.

Mitigation:Use replicated partitions with leader election to maintain availability and ordering. Implement retry logic in producer and consumer services to handle temporary queue unavailability.

Architecture Quiz - 3 Questions

Test your understanding

Which component ensures messages are processed in the order they were sent?

AMessage Queue (Partitioned with Ordering)

BLoad Balancer

CCache

DAPI Gateway

Design Principle

This architecture uses a partitioned message queue with ordering keys to guarantee that messages are processed in the exact order they were sent. By routing messages with the same key to the same partition, the system preserves sequence while scaling. Replication and retry mechanisms ensure reliability and availability.