The biggest issue was configuring the server to deal with files being uploaded and downloaded properly - many encoding issues and on top of that learning a new language (Go) to write it in. Dealing with time constraints was also a big challenge as we were dealing mostly with technologies we haven't used before (Go and Storj) so there had to be a trade off with scalable code for code that simply worked in the moment which can gladly be changed before ever deploying the app to the public.