Design a High-Concurrency Ticketing/Flash-Sale System
You are tasked with designing the backend for a limited-seat flash sale system, such as for concert tickets. This system must accommodate millions of concurrent purchase attempts while ensuring strict inventory correctness (no overselling), fairness, and resilience under extreme load. The design must also support short-term seat reservations and integrate with payment processing.
Requirements
1. Scale and Correctness
- The system must handle millions of concurrent purchase attempts.
- Strict inventory correctness is paramount: no overselling of seats or SKUs.
- Real-time availability of seats/SKUs must be exposed to users.
2. Fairness and Backpressure
- Implement a mechanism to ensure fairness, such as a FIFO queue or a lottery system, for purchase attempts.
- The system should incorporate queueing with backpressure and rate limiting to manage load.
3. Purchase Flow
- Support short-term reservations for seats/SKUs, which expire after a defined payment timeout.
- Order creation must be idempotent to allow for safe retries without duplicate processing.
4. Reliability and Performance
- Include anti-bot protections to prevent abuse.
- Design for sharding of "hot items" (e.g., popular tickets) to distribute load.
- Detail the read and write paths, including choices for caches and databases.
- Specify the consistency model and a reconciliation strategy for potential inconsistencies.
- Outline failure handling mechanisms.
- Provide capacity planning assumptions and calculations.
- Describe the load testing methodology and define Service Level Objectives (SLOs).
Deliverables
Your design should cover the following aspects:
- APIs: Sketch out key endpoints, including request and response structures.
- Data Model: Define core entities and their primary/secondary keys.
- Read and Write Paths: Illustrate the flow of data for both read and write operations.
- Cache/DB Choices: Justify the selection and usage of specific caching and database technologies.
- Message Queues: Describe the role of message queues, including topics and their applications.
- Consistency Model & Reconciliation: Explain the chosen consistency model and how reconciliation will be performed.
- Failure Handling: Detail strategies for handling various system failures and fallbacks.
- Capacity Planning: Present assumptions and calculations for scaling the system.
- Load Testing & SLOs: Outline the approach to load testing and the defined SLOs for the system.
AI interview prep
Core dilemma
Balancing extreme write concurrency and throughput with strict, global inventory correctness and fairness under peak load, while maintaining system resilience and preventing overselling.
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 High-Concurrency Ticketing/Flash-Sale System
You are tasked with designing the backend for a limited-seat flash sale system, such as for concert tickets. This system must accommodate millions of concurrent purchase attempts while ensuring strict inventory correctness (no overselling), fairness, and resilience under extreme load. The design must also support short-term seat reservations and integrate with payment processing.
Requirements
1. Scale and Correctness
- The system must handle millions of concurrent purchase attempts.
- Strict inventory correctness is paramount: no overselling of seats or SKUs.
- Real-time availability of seats/SKUs must be exposed to users.
2. Fairness and Backpressure
- Implement a mechanism to ensure fairness, such as a FIFO queue or a lottery system, for purchase attempts.
- The system should incorporate queueing with backpressure and rate limiting to manage load.
3. Purchase Flow
- Support short-term reservations for seats/SKUs, which expire after a defined payment timeout.
- Order creation must be idempotent to allow for safe retries without duplicate processing.
4. Reliability and Performance
- Include anti-bot protections to prevent abuse.
- Design for sharding of "hot items" (e.g., popular tickets) to distribute load.
- Detail the read and write paths, including choices for caches and databases.
- Specify the consistency model and a reconciliation strategy for potential inconsistencies.
- Outline failure handling mechanisms.
- Provide capacity planning assumptions and calculations.
- Describe the load testing methodology and define Service Level Objectives (SLOs).
Deliverables
Your design should cover the following aspects:
- APIs: Sketch out key endpoints, including request and response structures.
- Data Model: Define core entities and their primary/secondary keys.
- Read and Write Paths: Illustrate the flow of data for both read and write operations.
- Cache/DB Choices: Justify the selection and usage of specific caching and database technologies.
- Message Queues: Describe the role of message queues, including topics and their applications.
- Consistency Model & Reconciliation: Explain the chosen consistency model and how reconciliation will be performed.
- Failure Handling: Detail strategies for handling various system failures and fallbacks.
- Capacity Planning: Present assumptions and calculations for scaling the system.
- Load Testing & SLOs: Outline the approach to load testing and the defined SLOs for the system.