System requirements


Functional:

  • multiple parking spot sizes
  • give each car a spot and reserve it
  • remove car from reservation upon exit
  • calculate payment


Non-Functional:

  • consistent - no spot should have more than 1 car at a time



Capacity estimation

  • scalability should not be an issue, a parking lot or garage can only have ~1000 cars .
  • even with many garages, the number of cars going in and out is not too many





API design

POST /reservation

  • carType
  • entry time
  • returns spot ID


GET /payment/{spotID}

  • calculate payment


POST /payment/{spotID}

  • make payment
  • delete reservation



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...


2 Tables


  1. Reservations
  • Spot ID - Type - License Plate - Reservation Time
  1. Spots
  • Spot ID - Type (index)



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...


Consistency over avaialbility

  • its ok if the system goes down for a while, cars can wait
  • but 2 cars cannot park in the same spot


can use locks to prevent 2 requests for same spot


Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.


  • many requests to the DB
    • can intro a cache to take booked reservations



Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?