May 15, 2022 6:00 PM PDT
This document summarizes the design and discussion of an online ticket system, focusing on functional and non-functional requirements, system architecture, and various design considerations.
Requirements
Functional Requirements
- Movie Ticket System
- Support for different locations (Cities, Cinemas, Rooms)
- User login functionality
- Movie search capabilities
- Cart functionality for selected movies
- Seat selection
- Payment processing
- Conflict resolution for seat selection (handling simultaneous requests)
Non-Functional Requirements
- User capacity: 1 million visits per day
- Ticket sales: 100,000 tickets per day
- Total cinemas: 100
- System scalability: Must scale quickly within a limited timeframe
Additional Functional Requirements
- Notification system for available seats
- High peak traffic handling (e.g., popular movies sold within 2 minutes)
System Design
System Architecture
- Database Choices
- MySQL selected for its low QPS and convenience.
- Consideration of data balancer and caching to reduce read loads.
Service Design
- Multiple services are required for searching tickets and ordering tickets.
- Implementation of a hold mechanism for tickets (hold time and expiration).
- API requirements for cron jobs to manage ticket availability.
Scalability Considerations
- Horizontal scaling options if the number of cinemas increases significantly.
- Use of NoSQL databases for scalability.
Payment Handling
- Implementation of ACID properties to manage payment failures and ticket status.
- Notification mechanisms for users when previously unavailable tickets become available.
Monitoring and Improvements
- Establish a monitoring system for database performance, payment processing, and search functionalities.
- Tracking user behavior for business insights.
Feedback
Interviewer Feedback
- Overall performance met L4 requirements.
- Requirement gathering was clear, but system design drawings lacked clarity in some areas.
- Suggested improvements in detail, particularly in database schema design and trade-offs.
Audience Feedback
- Clarification of requirements was needed before jumping into object-oriented design.
- Time constraints affected the depth of detail in the design.
Hard Skill Insights
- Discussion on splitting databases for tickets and transactions, requiring a coordinator service.
- Consideration of microservice architecture for scalability and reliability.
- Preference for saga orchestration over 2PC for distributed transactions due to external system interactions.
Conclusion
The design discussion highlighted the importance of clear requirements, effective system architecture, and the need for robust handling of transactions and scalability in an online ticketing system.