How much data should I store in an object locally Trying to limit requests to database

Question

I'm now downloading pictures from my S3 account on AWS. The problem is that I will be requesting numerous photos, which inevitably results in numerous requests.

I've been thinking about collecting a list of all the photos I require as soon as the app launches and saving them in an object so that I can later filter the images I require throughout the app. This would reduce the number of calls I make.

My inquiries are:

How much information can be stored locally before performance suffers?

Is scalability something I should be worried about, or do I just have to bear the expense? How does Instagram handle all of its pictures? Do they have a lot of demands?