System requirements

Functional:

List functional requirements for the system (Ask the chat bot for hints if stuck.)...

User can reserve a parking spot.

User pays for the reservation

User can park a car on the parking lot

User can leave before the reservation time expires.

User can be absent with reservation, and we may charge it

Non-Functional:

List non-functional requirements for the system...

Scalability

Availability

Consistency

Capacity estimation

Assumption:

20 countries, 100 parking lots for each one

we do both short term and long term and only 20% user do long term parking.

Each parking lots has 200 parking spots

Each parking lots receives 400 reservations per day

20 * 100 = 20000 parking lots

2000 * 400 = 800000 reservations a day

each reservation would be:

reserve id (8 bytes)

userId (8 bytes)

car type (1 byte)

Reservation start time (8 bytes)

Reservation end time (8 bytes)

API design

Define what APIs are expected from the system...

List getLot(optional_cur_location)

List check_capacity(lot_id, vehicle_type, start_date_time, end_date_time)

reserve_ID reserve_spot(auth_token, user_id, lot_id, vehicle_type, start_date_time, end_date_time)

vehicle_arrived(reserve_id)

vehicle_left(reserve_id)

Database design

Reservation Table

reservation_id (primary_key)

sport_id (foreign_key)

user_id (foreign_key)

vehicle_id (foreign key)

start_time

end_time

Payment Table

payment_id (primary key)

user_id (foreign_key)

payment_status

update_time

Sport Table

sport_id

lot_id

status

spot_num

Lot Table

lot_id

contact_id

vehicale table

vehicle_id (primary key)

user_id (foreign key)

vehicle_type

plate_numer

parking_staus table:

status_id

status

check_in

check_out

user_id

vehicle_id

High-level design

client -> payment

client -> api_gateway

api_gateway -> reservation_service -> database

api_gateway -> parking_staus -> database

status_monitoring -> database

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...

it will first call getLot or view lot on local/remote cache

if user click on any lot, it will allow user to reserver with reserve_spot

it will redirect user with payment service and create a reserve_spot request, if payment is made and being called from payment service by call back with a transaction_id, it will process the payment

it can be failed under below cases:

1. user failed to make payment
2. conflict with existing reservation
3. a race condition that not spot in the lot

mointor service peroidically check the databse for status and collect payment for absent users

if there is a wrong state happend such as vehicle try to left when it never left or it over stay, the admin will be notified or maybe some auto action will be excuted base on exsiting rule

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?