Chat Messaging System Design (FB Messenger, WhatsApp)
Introduction
Chat messaging platforms like Facebook Messenger and WhatsApp enable real-time communication for billions of users. These systems must support both persistent (stored) and non-persistent (ephemeral) messaging with high reliability and low latency.
Problem Statement
How can we design a chat system that supports real-time messaging, message history, and high availability at global scale?
System Requirements
- Real-time message delivery.
- Message persistence (for Messenger) or ephemeral delivery (for WhatsApp).
- Group chats and media sharing.
- Scalability and fault tolerance.
- End-to-end encryption.
High-Level Design
The system consists of:
- Client Applications: Send and receive messages.
- Message Broker: Routes messages between users.
- Database: Stores message history (for persistent chat).
- Notification Service: Alerts users of new messages.
- Encryption Layer: Secures messages in transit and at rest.
Key Components
- WebSockets: Enables real-time, bidirectional communication.
- Message Queues: Buffers and routes messages.
- Replication: Ensures message durability and availability.
- Delivery Receipts: Tracks message status (sent, delivered, read).
Challenges
- Scalability: Billions of messages per day.
- Consistency: Ensuring message order and delivery.
- Reliability: Handling network failures and offline users.
- Security: End-to-end encryption and privacy.
Example Technologies
- Brokers: Kafka, RabbitMQ, custom solutions.
- Databases: Cassandra, DynamoDB, MongoDB.
- Protocols: WebSocket, MQTT.
Conclusion
Building a chat messaging system requires efficient real-time communication, robust storage, and strong security. By leveraging scalable brokers, databases, and encryption, you can deliver a seamless messaging experience.