System requirements

Functional:

users are able to check remaining spots in real time;

remaining spots are updated when vehicles enter & exit the parking lot

Non-Functional:

100 ~ 200 peak read qps

reliable, scalable

read consistency doesn't have to be strong (users can get slight outdated data)

Capacity estimation

100 ~ 200 peak read qps

support ~ 500 vehicles maximal

~50 parking lots

takes about 1 min for a vehicle to enter or leave a parking lot, so write qps is at most 50 * 2 (because enter + exit) / 60 = 1.67, which is relatively low

API design

REST APIs for write (enter & leave parking lot)

/v1/enter

request: {

Enum vehicleType (can be car, motorbike, van),

Int parkingLotId

}

response {

boolean successful

}

/v1/exit

request: {

VType vehicleType (can be car, motorbike, van),

Int parkingLotId

}

response {

boolean successful

}

Read API

long poll

checkAvailableSpots

request {

list parkingLotIds

}

response {

Map> parkingLotRemainingSpots

}

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...

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...

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?