How to securely integrate Dropbox API keys in Shopify?

[ttttt42]

New to shopify, comfortable with code.

Not sure if I'm asking in the right place.

Need to create a page with a couple of dropdowns, which pull a file from a dropbox folder determined by the dropdown choices.

Where do I put the dropbox API keys so they aren't publicly accessible? 

They'd normally go server-side. Is this possible in the normal code editor, or do I need to start building a private app?

Thanks!

[ttttt42]

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