Architect a high-throughput Chat Engine
Last updated: October 22, 2025
Quick Overview
Design a high-throughput chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
ServiceNow
October 22, 20253
5
1,033 solved
Design a high-throughput chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from ServiceNow's System Design Round tests whether you can reason about software design at a deep level. The interviewer expects discussion of maintainability, testability, and operational considerations.
What the Interviewer Expects
- Apply engineering principles to a realistic design scenario
- Discuss trade-offs between different approaches with concrete examples
- Demonstrate understanding of testability, maintainability, and extensibility
- Connect theoretical concepts to production engineering practices
- Discuss how the approach scales with team and codebase size
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
- How would this design change if the team size doubled?
- How would you measure the performance of this component in production?
- What testing strategy would you use for this component?
- What are the security implications of this design?
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Core Design Principles
For a high-throughput chat engine, several core design principles are critical:
- Separation of Concerns: This principle ensures that different aspects of the chat system (message handling, user ...
Architecture
The architectural approach for the chat engine will be a microservices architecture, leveraging technologies such as WebSockets for real-time communication and a distributed database like Apache Cassa...
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