Don’t forget that Elixir is a fantastic ‘glue’ language between languages as well, it’s Ports and Nif’s are not to be discounted. 
Well the first decision is what protocol to use, like do you want to use a standard protocol like HTTPS or SFTP, or do you want some custom protocol inside an SSL connection? If you just want something secure and fast then the beam has a built-in SFTP module, the server documentation of which is at: ssh_sftpd — OTP 29.0.2 (ssh 6.0.1)
If using https then cowboy/plug/phoenix (depending on what extra functionality and features you want, and what kind of clients will be pulling it) will work well.
Though more information and details can be given if this can be filled out.
- What client(s) do you want pulling from it (something prebuilt and if so what, or will you make it yourself)?
- What protocol(s) do you want to use (something pre-defined, or making something custom)?
- What do you want the BEAM server to do that something like an SFTP server itself cannot do?
- Etc… anything else that might be relevant.
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,. The checksum is ok, with severam encoding choices, thanks to streaming, is ok):