Architect a multi-tenant Messaging Engine

Last updated: June 13, 2026

Quick Overview

Design a multi-tenant messaging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Zoom
System Design
Software Engineer
Zoom
June 13, 2026
Software Engineer
Technical Screen
System Design
Hard

360

12

1,926 solved


Design a multi-tenant messaging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Zoom asks this during the Technical Screen to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.

What the Interviewer Expects
  • Drive the design discussion proactively with minimal interviewer guidance
  • Perform detailed capacity estimation and use it to inform design decisions
  • Design for global scale with multi-region deployment and data consistency
  • Deep dive into 2-3 critical components with implementation-level detail
  • Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
  • Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
  • Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Partitioning and sharding strategies
Load balancing and horizontal scaling
Requirements gathering and capacity estimation
High-level architecture and component design
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • What monitoring and alerting would you set up on day one?
  • What would the deployment pipeline look like for this system?
  • How would you handle schema migrations with zero downtime?
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Sample Answer
Requirements

Functional Requirements

  1. Multi-tenant Support: The messaging engine should support multiple tenants (different organizations) with strict data isolation.
  2. Real-time Messaging: Users sh...
Capacity Estimation

Assuming Zoom has around 300 million active users, and estimating that approximately 10% (30 million) are using the messaging feature concurrently:

  • Messages per second: If each user sends an ave...

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