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HLDsystem_design~12 mins

WebSocket for real-time communication in HLD - Architecture Diagram

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System Overview - WebSocket for real-time communication

This system enables real-time, two-way communication between users and servers using WebSocket technology. It supports instant message delivery, low latency updates, and scalable connections for many users simultaneously.

Architecture Diagram
User
  |
  v
Load Balancer
  |
  v
WebSocket Server Cluster
  |
  +----------------+
  |                |
Cache (Redis)   Message Broker (Kafka)
  |                |
  v                v
Database         Notification Service
Components
User
client
Initiates WebSocket connection and sends/receives real-time messages
Load Balancer
load_balancer
Distributes incoming WebSocket connection requests evenly across servers
WebSocket Server Cluster
service
Maintains WebSocket connections, handles message routing and session management
Cache (Redis)
cache
Stores frequently accessed session data and recent messages for quick retrieval
Message Broker (Kafka)
message_queue
Manages asynchronous message delivery and event streaming between services
Database
database
Persists user data, message history, and connection metadata
Notification Service
service
Sends push notifications or alerts based on real-time events
Request Flow - 8 Hops
User → Load Balancer
Load Balancer → WebSocket Server Cluster
WebSocket Server Cluster → Cache (Redis)
User → WebSocket Server Cluster
WebSocket Server Cluster → Message Broker (Kafka)
Message Broker (Kafka) → Notification Service
Notification Service → User
WebSocket Server Cluster → Database
Failure Scenario
Component Fails:Load Balancer
Impact:All incoming WebSocket connection requests fail, causing service unavailability for new connections.
Mitigation:Use multiple load balancers with failover and health checks to ensure high availability.
Architecture Quiz - 3 Questions
Test your understanding
Which component handles the initial WebSocket connection request from the user?
AWebSocket Server Cluster
BLoad Balancer
CMessage Broker
DCache
Design Principle
This architecture uses a load balancer to distribute WebSocket connections, caches to speed up session data access, and a message broker to handle asynchronous event processing. This design supports scalable, low-latency real-time communication with fault tolerance and separation of concerns.