- Do I have to have www. in my URL?
- In short, yes. Due to how DNS works and how the foo//bar service is hosted.
The long answer is because the foo//bar service makes use of CNAMEs for load-balancing and due to the volatility of IP addresses in cloud deployments.
A CNAME must be specified as a host record (e.g. the www host in the example.com domain: www.example.com), an apex record must be an A record (an IP address). The IP addresses of foo//bar servers are volatile and can change without notice.
It doesn’t have to be .www, but does have to be a host record; e.g. www.example.com, foo.example.com, bar.example.com are all hosts, example.com is not).