System requirements
Functional:
- Use should be able to see nearby Movie theaters.
- User should be able to see movies list in each theater.
- User should be able to select movie and seat for the ticket.
- The ticket should hold for the user for 5 ~ 10 minutes to complete payment.
- User should be able to complete the payment.
Non-Functional:
- Availability
- Scalability
- Strong consistency for movie ticket counts.
- mid level Latency. Checking ticket availability and completing payment could be allowed around 10 second delay.
Capacity estimation
Assume the system has 10m DAU.
Read QPS: 10m / 100k = 100
The peak read QPS will be twice the traffic: 2 * 100 = 200
Assume 1% user buy one ticket per day.
Write QPS: 10m * 1% / 100k = 1
The peak write QPS will be twice the traffic: 2 * 1 = 2
So this is a read heavy system.
API design
GET
Database design
Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...
High-level design
You should identify enough components that are needed to solve the actual problem from end to end. Also remember to draw a block diagram using the diagramming tool to augment your design. If you are unfamiliar with the tool, you can simply describe your design to the chat bot and ask it to generate a starter diagram for you to modify...
Request flows
Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...
Detailed component design
Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...
Trade offs/Tech choices
Explain any trade offs you have made and why you made certain tech choices...
Failure scenarios/bottlenecks
Try to discuss as many failure scenarios/bottlenecks as possible.
Future improvements
What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?