Design Notification Infrastructure for mobile apps
Last updated: November 16, 2025
Quick Overview
Design a multi-tenant notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Datadog
November 16, 202530
7
2,720 solved
Design a multi-tenant notification system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from Datadog'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
- 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 you document this for other engineers?
- How would you measure the performance of this component in production?
- What testing strategy would you use for this component?
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Core Design Principles
For the multi-tenant notification system, the following core design principles apply:
- Separation of Concerns: Each component (e.g., message generation, delivery, logging) should focus on a spe...
Architecture
The architecture for the notification infrastructure will adopt a microservices approach, leveraging the following components:
- Notification Service: This service handles the creation and queui...
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