I see two possible solutions. First, as @moogle19 suggested, you can use NumbleCSV’s parse_stream and send a chunked response using Plug.Conn.send_chunked/2, never loading the whole file into memory. Second, you can, again, use parse_stream to stream the contents into a temporary file and use Plug.Conn.send_file/5. I believe the second one is trickier because in case you have a lot of requests there should be rate limiting in order to not fill your disk memory.
