200 spots parking lot, 500 cars per day.
1 server is enough, with load balancer
park(spot) //choose a spot to park
leave(spot)// choose a spot to leave
sql
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...
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...
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...
sql/ non-sql databases
too many cars
expand the parking lot