Hey community!

I successfully deployed a domain and provisioned two redundant DNS hosting instances, initially everything was humming along, but the following day, my site went dark.

Meanwhile, other content is still accessible.

Could it be that the DNS propagation hasn't completed yet, or is there another issue at play?

DNS propagation. It's a common misconception that DNS propagation is a one-time event that occurs when you set up your domain. In reality, DNS propagation is an ongoing process that can take anywhere from a few minutes to several hours or even days to complete, depending on the complexity of your setup and the speed of your DNS providers.

However, in your case, since other content is still accessible, it's unlikely that DNS propagation is the sole culprit. There's likely another issue at play, and I'm going to take a stab in the dark and say that it's probably related to your DNS hosting instances.
I can tell you that DNS hosting instances can be a real pain to troubleshoot, especially when you're dealing with redundancy. It's possible that one of your instances has gone down or is experiencing some kind of connectivity issue, which is causing your site to become inaccessible.

But before you start panicking, let's take a step back and think about the bigger picture. Are you using a load balancer or some kind of DNS failover mechanism to ensure that your site remains accessible even if one of your instances goes down? If not, that could be a contributing factor to your site's sudden disappearance.

I'd recommend checking your DNS hosting instances' logs to see if there are any errors or issues that could be causing the problem. You should also check your domain's DNS records to ensure that they're configured correctly and that there are no typos or other errors that could be causing issues.
I'd say that it's always a good idea to have a backup plan in place, just in case something goes wrong. Whether it's a secondary DNS hosting instance or a load balancer, having a backup plan can help minimize downtime and ensure that your site remains accessible to your users.

What exactly is a domain zone? Additionally, it's possible that updates haven't been made or there are issues with the hosting provider.

I'd recommend firing up a tool like NSLookup or Dig to drill down to the root cause of the problem. By pinging the site and analyzing the DNS response, we can identify which DNS servers are authoritative for the domain and which ones are returning the site. This will give us a better understanding of the DNS infrastructure and help us pinpoint the issue. Additionally, we can use tools like Whois or DNSstuff to gather more intel on the domain and its DNS configuration. By taking a closer look at the DNS records and server responses, we should be able to isolate the problem and get the site up and running in no time.