Rate Limit Dropbox API in Web application.

The API was designed with the intention that each user would link their own Dropbox account, in order to interact with their own files. However, it is technically possible to connect to just one account, as you've shown here.

We generally don't recommend doing so, for various technical and security reasons. For instance, the Dropbox API rate limiting system is built for the scenario where each user connects their own account. The rate limits operate on a per-Dropbox user account basis. 

So, if you run all of your users through your single Dropbox user account, you are more likely to run in to rate limits. There isn't a supported better way to do this via the API, such as registering more keys/tokens or re-using a client, since it's per-Dropbox user account.

One alternative may be to access the Dropbox shared link directly, using one of the URL parameters documented here. That way, you wouldn't be using the API and be subject to the API rate limits. You would still be subject to the shared link bandwidth limits though. In general though, it sounds like your use case may be better suited by a general CDN, as opposed to Dropbox.