Design in case of aggregator

Websites like bookmyshow, paytm are aggregator platforms which deal with multiple theaters / cinemas to provide ticket booking to the clients. The current design focuses more on scenario where in we want to design for a platform that maintains all the theaters and movie information.

How would we design in such scenarios?
Couple of use-cases:

  1. User in paytm and a user in bookshow try to book a same seat.
  2. How the aggregator platform would know about the status of availability of tickets for a particular movie and show. They need to continuously poll the theaters servers to get the latest info?