There are several ways to solve this:
1. Save it to a file
See this post to get an idea of how to write data to files
2. Use the Kirby cache
See the post above in the same threat
3. Save it to a custom site field
This is something a did a while ago. You need a textarea field to store the data and a textarea to store the timestamp of last update. And then you need to check if the data should be read from the field or if a new request should be made.