System requirements

Functional:

1. Entry ticketing
2. Exit ticketing with payment based on hours parked
3. Login
4. Search by venue
5. Determine free slots
6. Reserve slots
7. Payment processing
8. View/modify reservation
9. View per user history

Non-Functional:

Performance: Quickly identify free slot as soon as vehicle exits lot. Low latency < 2ms for server to respond

Availability : Ensure uptime so that service is available at all times

Security: Authentication.

Capacity estimation

1M total users

100K active daily users

10K concurrent users

API design

REST API

1. Login: POST v1/login
2. View Location: GET v1/search?location=<location>&date=<date>&timerange=<timerange>
3. Reserve slot: POST v1/reserve?location=<location>&date=<date>&timerange=<timerange> returns reservationid
4. Cancel slot: POST v1/cancel?reservationid=<reservationid>
5. Payment: POST v1/payment?reservationid=<reservationid>
6. View history: GET v1/history?userid=<userid>

Database design

Database tables :

User table: [id, name]

Location: [venue, capacity, type]

Reservation: [ id, userid, venue, type, payment status, payment id, date,time range]

Payment : [payment id, charges,date, time]

High-level design

User logins via API Gateway to servers which are load balanced.

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?