HubSpot Software Development Engineer interview questions

Create an API from scratch that takes user names, emails, one country they could attend and what dates they could attend that country. Find which dates for each country that the most people could attend in two consecutive days and return the dates as strings that they would be attending them. POST the countries with the dates as JSON properties to their server until you get a status of 200. The resulting JSON they're looking for does not match the example result provided.