System requirements

Functional:

1. Reservation:
   • Users can reserve a parking spot through the system.
   • Users can complete the reservation by making a payment.
2. Parking Management:
   • Allocate parking spots based on user reservations.
   • Handle different vehicle types.
3. Entry and Exit Management:
   • Track vehicle entry and exit from the parking lot.
4. Error Handling:
   • Address scenarios where users make reservations but don’t show up, possibly charging a fee for the first 24 hours.

Non-Functional:

Performance(latency, hight throughput), scalability(vertical/horizontal), availability, security, reliability, consistency etc

Capacity estimation

Number of parking lots = 1000

Parking lot capacity = 200

Reservation requests = 200 * 1000 = 200 000

API design

API used by user:

checkCapacity(lot_id, vechile_type, start_time, end_tine) [is_free, price] - checks if parking lot has a free spot and returns price

reserveSpot(user_id, lot_id, vechile_type, start_time, end_time) -

returns reservation_id and price. Also forwarded on 3d party payment system.

completeReservation(reservation_id, payment_token) - after payment we need to complete payment procedure

API used by parking lot:

vechile_arrived(reservation_id, time)

vechile_left(reservation_id, time)

Database design

Reservation table:

• Reservation_id(key)
• Spot_id(foreign key)
• User_id(foreign key)
• Payment_status
• Start_time
• End_time
• Stuts

User table:

• User_id(key)
• Contact_info

Vechile table:

• vechile_id(key)
• user_id(foreign key)
• type

Spot table:

• Spot_id(key)
• Lot_id(foreign key)

High-level design

Parking lot - notifies when car arrive or left

Client - user , that wants to get parking spot

Api gateway - mediator fro http requests

Reservation service - checks for empty place and update reservation in database

Payment service - 3d party for payments

Request flows

checkCapacity request handles by reservation service. It checks if we have an empty spot.

reserveSpot request - handles by reservation service. Adds. a new reservation in the system and redirect user for payment service.

completeReservation - after payment, user confirms that spot was paid by token.

vechile_arrived - notifies, when car arrived on parking lot.

vechile_left- notifies, when car left from parking lot.

Detailed component design

For reservation we can use first fit slot allocation or time-slot reservation with time intervals

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?