Setting up Discourse with SSL on Docker with AWS ELB breaks and returns 503 Service Unavailable (Back-end server is at capacity)

Make the directory. Although, actually, as of today, that directory will be made for you now.

Also, I believe that various research indicated that spying is being done on unencrypted backend connections. You should have SSL all the way through, even if on self-signed certs as long as the cert sha-2 fingerprint is verified.