Was asked this database design question in one of the interview for the role of an SDE Intern.
Design an online support desk application:
Requirements :

1. Companies can register to our application.
2. N number of agents can be associated to each company registered.
3. Users use our application to communicate with the agent for a issue with a company product. Ticket to track each problem.
4. Our application allocates the user to appropriate agent.
5. Handle holidays and leaves of agent.

I was expected to come up with entities (Agents, Company, Users, Ticket etc. ) for which table will be created in a database , their primary keys , suitable datatypes for the attributes etc. and was asked few SQL question based on the design .