I do for myself, the site - the withdrawal of currencies from different banks, a calculator for convection. And so there were a few questions about how to do it.
Firstly, I take the data about the course from the API of another site, each time sending a request, what makes the loading of the site very long, how to optimize this process? Write data to the database every n minutes to update them, and then output to the user? Or the load can not be avoided?