Design a Scalable End-to-End Encrypted (E2EE) Messaging System

End-to-End Encrypted Messaging System

Design a high-scale, end-to-end encrypted (E2EE) messaging platform similar to Signal or WhatsApp. The system must support 100M daily active users, providing real-time delivery for online users and reliable store-and-forward delivery for offline users. Key requirements include implementing a mechanism for asynchronous key exchange (X3DH), ensuring perfect forward secrecy via the Double Ratchet algorithm, and handling encrypted media uploads. Discuss how you would minimize metadata leakage, handle presence at scale, and ensure no messages are lost during server-side failures.
Signal ProtocolWebSocketsKafkaRedisPostgreSQLCassandraS3gRPCTLS 1.3JWT
00
Read

Design a Scalable End-to-End Encrypted (E2EE) Messaging System

Design a secure, real-time messaging application similar to Signal or WhatsApp that supports end-to-end encryption for 10 million daily active users. The system must handle asynchronous messaging (offline recipients), provide perfect forward secrecy, and ensure the server cannot access message content. Discuss the key exchange protocol (X3DH/Double Ratchet), scaling persistent connections, and the trade-offs involved in metadata privacy versus operational visibility.
WebSocketsSignal ProtocolX3DHDouble RatchetDynamoDBCassandraRedisKafkaS3AES-256
00
Read
1
InterviewGPT

AI-powered tools to help you succeed in tech interviews — from resume to offer.

Interview Solver

  • Coding Puzzles
  • System Design
  • Behavioral Challenges
  • ML System Design
  • SQL Puzzles
  • FE System Design
Explore Solver

Question Bank

  • Coding Interview Questions
  • System Design Interview Questions
  • Behavioral Interview Questions
  • ML System Design Questions
  • SQL & Database Questions
  • FE System Design Questions
Explore Questions

Golden Blogs

  • Coding Solutions
  • System Design Guides
  • Behavioral Guides
  • ML System Design Guides
  • SQL Solutions
  • FE System Design Guides
Explore Blogs

Intervipedia

  • Coding Concepts
  • System Design Concepts
  • Behavioral Concepts
  • ML System Concepts
  • SQL Concepts
  • FE System Concepts
Explore Concepts

Application Tools

  • Self-Intro Generator

Company

  • Pricing
  • FAQ
  • About
  • Privacy Policy
  • Terms of Service

© 2026 InterviewGPT Inc. All rights reserved.

All systems operationalUS-East

Made with ♥ for developers