Design WhatsApp
Last updated: January 14, 2026
Quick Overview
Design the architecture for WhatsApp. Cover scalability, data storage, caching, and real-time requirements.
Meta
January 14, 2026100
4
3,644 solved
Design the architecture for WhatsApp. Cover scalability, data storage, caching, and real-time requirements.
Meta asks this during the Onsite to assess your depth in software engineering. They want to see understanding of design patterns, system architecture, and the trade-offs involved in different technical approaches.
What the Interviewer Expects
- Design a complex system component applying multiple engineering principles
- Reason about system-level trade-offs: performance, reliability, developer experience
- Discuss advanced patterns: event sourcing, CQRS, distributed transactions
- Address cross-cutting concerns: observability, security, backward compatibility
- Demonstrate depth in both theoretical foundations and practical implementation
Key Topics to Cover
How to Approach This
- Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
- Choose data structures based on access patterns, not familiarity.
- Prefer immutable data and message passing over shared mutable state for concurrency.
- Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
- What are the security implications of this design?
- What testing strategy would you use for this component?
- How would you handle backward compatibility?
- How would you measure the performance of this component in production?
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Core Design Principles
For designing WhatsApp, we will adhere to the following core design principles:
- Scalability: The system must handle millions of concurrent users and messages. This requires a distributed archi...
Architecture
The architecture for WhatsApp will be microservices-based and include the following components:
- Client Application: Mobile and web clients for messaging. They will utilize WebSockets for real-...
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