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Design a configurable monthly API rate limiter
Distributed CountersRate Limiting AlgorithmsDistributed Systems Consistency ModelsIdempotency and RetriesTime Zones and Scheduling
Problem Description
Design a distributed rate-limiting system for an expensive API. This system must enforce monthly quotas for individual users or API keys.
Requirements
- Each user or API key is assigned a monthly quota (e.g., 10,000 calls/month).
- Users must be able to manually configure and update their monthly quota through a UI or API.
- Upon exceeding their allocated quota, a user's subsequent API requests must be rejected, typically with an HTTP 429 status code, until the quota resets at the beginning of the next month.
Scale & Reliability
- The system should be designed to handle high Queries Per Second (QPS) across multiple stateless API servers.
- The rate limiter must function correctly in a distributed environment.
- Candidates should discuss the trade-offs between strict and eventually consistent correctness goals for the rate limiting mechanism.
Deliverables
- A high-level architectural overview and the request flow through the system.
- Proposed data models and storage choices for both API call counters and quota configurations.
- A detailed explanation of how monthly quota resets are handled, including considerations for time zones, retries, and idempotency.
- Discussion of operational concerns, such as monitoring, potential failure modes, and strategies for preventing abuse.
AI interview prep
Core dilemma
Balancing accurate, distributed, and highly available monthly quota enforcement with the performance demands of high QPS, while supporting dynamic quota configuration and reliable monthly resets across time zones.
Mid-level signals3
Senior signals3
Red flags3
3 tradeoffs and 3 stress tests locked
Interview prep
Unlock the interviewer X-Ray rubric, tradeoff matrix, stress tests, clarifying questions, and key concepts.
Design a configurable monthly API rate limiter
Distributed CountersRate Limiting AlgorithmsDistributed Systems Consistency ModelsIdempotency and RetriesTime Zones and Scheduling
Problem Description
Design a distributed rate-limiting system for an expensive API. This system must enforce monthly quotas for individual users or API keys.
Requirements
- Each user or API key is assigned a monthly quota (e.g., 10,000 calls/month).
- Users must be able to manually configure and update their monthly quota through a UI or API.
- Upon exceeding their allocated quota, a user's subsequent API requests must be rejected, typically with an HTTP 429 status code, until the quota resets at the beginning of the next month.
Scale & Reliability
- The system should be designed to handle high Queries Per Second (QPS) across multiple stateless API servers.
- The rate limiter must function correctly in a distributed environment.
- Candidates should discuss the trade-offs between strict and eventually consistent correctness goals for the rate limiting mechanism.
Deliverables
- A high-level architectural overview and the request flow through the system.
- Proposed data models and storage choices for both API call counters and quota configurations.
- A detailed explanation of how monthly quota resets are handled, including considerations for time zones, retries, and idempotency.
- Discussion of operational concerns, such as monitoring, potential failure modes, and strategies for preventing abuse.