Requirements

Functional Requirements:

• Allow reservation of a parking spot.
• Process payment for the reservation.
• Enable parking of a car in the reserved spot.
• Support early departure before reservation time expires.
• Gate check-in/out.
• Handle no show.

Non-Functional Requirements:

List the key non-functional requirements (eg low latency, scalability, reliability, etc.)...

Capacity Estimation

Estimate the scale of the system. Consider daily active users, read/write ratio, storage requirements, bandwidth, and any relevant QPS calculations...

API Design

Define the APIs expected from the system. This is your chance to analyze and define the read and write paths so that you can come up with the high-level design...

Reserve:

GET /reserve/v1/uid

List /reserve/v1/uid

POST /reserve/v1

Gate:

GET /gate/v1/rid/

POST /gate/v1/rid/checkin

POST /gate/v1/rid/checkout

High-Level Design

Gateway: The entry point, also used for user authentication.

Reservation Service: Query the available parking slot from Database, and make reservation.

Queue: Reservation request is queued in Queue. Then fetch from Payment Service for processing.

Payment Service: Called 3rd party payment gateway to proceed the payment, and update the reservation status.

Gate Service: Update the reservation status when the physical car checkin/checkout.

Database Design

User Table:

UID int

CarNumber String

Reservation Table:

RID int

UID int

CarNumber String

ParkingID int

Payment_status String

ParkingSlot Table:

ParkingID int

Status String

Detailed Component Design

1. A reservation request sent to the Gateway & Auth user identity.
2. List available parking slots from DB.
3. Reserve the slots by updating Parkingslot table status to processing.
4. Send request to queue -> payment service
5. Payment succeed -> Update db
6. Checkin -> Gate service -> db
7. Checkout -> gate service -> db