Is it okay to store data temporarily on the server or is it safer to always save it in a database?

I'm currently playing around with some Amazon APIs. When the client makes a request to my server for some information about a product, my server makes yet another request to Amazon to retrieve that information. Since there is a lot of information, I'm hoping to store that information in server memory for the next client request rather than issue another request to Amazon (which is slow) or storing it in a database (because I don't need all the information, but I won't know what information I do need until the next client request tells me). Is this advisable or should I save it in the database to be safe?