WhatsApp-like Messenger — System Design

Objective

Design and implement a large-scale messaging system inspired by WhatsApp, focusing primarily on backend architecture and distributed-system concepts.

Current Status

🚧 Development phase — implementation is in progress.

See implementation/README.md for implementation details, local setup, and current limitations.

System Design and Plans

The system design documents and implementation plans are in docs/:

• Requirements
• Scope and assumptions
• Scale estimation
• API design
• Data model
• High-level design
• Detailed design
• Reliability
• Security
• Observability
• Future revision notes
• Topics to learn
• Cache plans and cache TTLs
• Design decisions

Scope

In Scope

• 1-to-1 messaging
• Group messaging
• Message delivery
• Delivery/read receipts
• Online/offline presence
• Multi-device support
• Media messages
• Push notifications

Out of Scope (Or For later phases)

• Voice/video calling
• Payments
• Stories
• Status updates
• End-to-end encryption implementation (initial design phase)

Design Process

• Requirements
• Scale estimation
• User flows
• API design
• Data model
• High-level architecture
• Detailed design
• Reliability
• Security
• Observability
• Capacity planning
• Implementation
• Load testing