HLDsystem_design~12 mins

Message delivery guarantees in HLD - Architecture Diagram

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System Overview - Message delivery guarantees

This system ensures messages sent between users or services are delivered reliably. It supports different delivery guarantees like at-most-once, at-least-once, and exactly-once to meet various application needs.

Key requirements include handling message loss, duplication, and ordering while maintaining scalability and fault tolerance.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Message Producer Service
  |
  v
Message Queue (Broker)
  |
  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, authentication, and routes to producer service

Message Producer Service

service

Accepts messages from users and publishes them to the message queue

Message Queue (Broker)

message_queue

Stores messages reliably and supports delivery guarantees

Message Consumer Service

service

Consumes messages from the queue and processes or delivers them

Database

database

Stores message metadata and delivery status for tracking and deduplication

Cache

cache

Speeds up access to recent message delivery states to reduce database load

Request Flow - 8 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Message Producer Service

Message Producer Service → Message Queue (Broker)

Message Queue (Broker) → Message Consumer Service

Message Consumer Service → Database

Message Consumer Service → Cache

Message Consumer Service → User

Failure Scenario

Component Fails:Message Queue (Broker)

Impact:Messages cannot be stored or delivered, causing message loss or delay

Mitigation:Use replicated queues with failover; retry producers on failure; persist messages on disk

Architecture Quiz - 3 Questions

Test your understanding

Which component ensures messages are stored reliably before delivery?

ACache

BMessage Queue (Broker)

CLoad Balancer

DAPI Gateway

Design Principle

This architecture demonstrates how to achieve reliable message delivery by combining a message queue for durability, services for processing, and caching for performance. It uses layered components to handle failures gracefully and meet different delivery guarantees.