Security: Ensuring that the download links are secure, using HTTPS, and protecting against hotlinking. Maybe using signed URLs that expire after a certain time if users need to authenticate via API keys or OAuth tokens.
Potential issues to consider: Large file sizes could lead to longer download times and higher bandwidth usage. Implementing progressive download or adaptive bitrate streaming might help, but for straightforward downloads, just making sure the server is optimized.
Download Management: Allowing users to pause and resume downloads, which requires the server to support byte-range requests. This is standard for HTTP servers, so setting up the appropriate headers (Accept-Ranges) would be necessary.
In that case, maybe focus on features like rate limiting downloads per user, IP-based throttling, and ensuring that the server can handle the traffic. Also, optimizing file delivery with a CDN would be crucial.