Design Rate Limiting Infrastructure for microservices
Last updated: October 30, 2025
Quick Overview
Design a multi-tenant rate limiting system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
DoorDash
System Design
Software Engineer
DoorDash
October 30, 2025Software Engineer
Onsite
System Design
Medium
41
11
457 solved
Design a multi-tenant rate limiting system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
DoorDash asks this during the Onsite 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
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
Security and authentication
Caching strategies (local, distributed, CDN)
Partitioning and sharding strategies
Database selection and data modeling
Message queues and async processing
API design and rate limiting
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How would you implement rate limiting to protect the system?
- How would you handle schema migrations with zero downtime?
- What monitoring and alerting would you set up on day one?
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Requirements
Functional Requirements
- Rate Limiting: Implement per-tenant rate limiting based on API keys, where limits can be configured per endpoint (e.g., 100 requests/minute for the checkout API). 2....
Capacity Estimation
Back-of-Envelope Calculations
- Total Daily Requests: Assuming DoorDash processes around 10 million orders per day, let’s consider 5 API calls per order on average, resulting in:
- Total Req...
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