Questions on the API Developer Portal regarding number of APIs:
The API Developer Portal does not have a limit for the number of APIs it can handle. Naturally however, performance can be a concern if there is insufficient resources allocated to the Portal to be able to handle the traffic it receives. The same logic goes for the API Gateway too. Performance is very dependent on environmental factors such as traffic volume, memory allocation, CPU allocation, policy design, and much more. This is why proper load testing must be completed prior to publishing anything in a production environment.