Design Chat Infrastructure for real-time analytics
Last updated: February 14, 2026
Quick Overview
Design a event-driven chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
HRT
February 14, 202684
5
942 solved
Design a event-driven chat system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from HRT's Onsite 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
- 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?
- How would you document this for other engineers?
- How would this design change if the team size doubled?
- How would you handle backward compatibility?
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Core Design Principles
For the event-driven chat infrastructure, the core design principles that apply are:
- Separation of Concerns: This principle ensures that different functionalities of the chat system (user inte...
Architecture
The architectural approach for this chat infrastructure will be based on a microservices architecture utilizing an event-driven model:
- Components:
- Message Broker: Use Apache Kafka for...
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