Design a Caching for Twitter/X
Last updated: February 19, 2026
Quick Overview
Design a multi-tenant caching system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Twitter/X
February 19, 202637
6
3,323 solved
Design a multi-tenant caching system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from Twitter/X'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
- How would you handle backward compatibility?
- What testing strategy would you use for this component?
- How would you document this for other engineers?
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Core Design Principles
In designing a multi-tenant caching system for Twitter/X, the following core design principles are paramount:
- Separation of Concerns: This principle allows us to isolate the caching mechanism ...
Architecture
The proposed architecture for the caching system utilizes a distributed in-memory cache like Redis or Memcached, designed to support multi-tenancy:
- Cache Layer: This layer handles all cach...
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