Revisiting DNS After Years: What a 10-Year Engineer Had Forgotten

I was trying to publish my new service "DevLoopRunner" to the internet and register it with Google Search Console.

I opened the DNS settings page, and my hands stopped.

"Wait, what do I put in the Host Name field...?"

I'll be honest. Even after 10 years as an engineer, DNS is something I forget because I don't touch it often.

I've worked on infrastructure-heavy projects and configured Route 53 several times. But it's not something I deal with daily. So when I finally need to touch it again, I find myself thinking, "How did this work again?"

This time, I reorganized my DNS knowledge while chatting with ChatGPT, so I'm documenting the process. Hopefully, it'll help others who "kind of know it but are a bit fuzzy on the details."

The Trigger: Registering a Domain Property in Search Console

When registering a site in Google Search Console, if you choose "Domain property," you're asked to set up a DNS TXT record.

The screen shows a verification string, and you just need to register it in DNS.

...But I got stuck on what to put in the "Host Name" field.

The Answer: Host Name Is "@" or Empty

The answer was simple.

"@" represents the root of the DNS zone (the domain itself).

For example, if you're managing example.com, then @ = example.com.

Common Mistakes

This is a surprisingly common trap.

Understanding What "@" Really Means

I'm a bit embarrassed to admit I didn't fully understand what "@" meant.

In DNS management interfaces, this calculation happens:

Host + Zone = FQDN (Fully Qualified Domain Name)

So:

"@" is a symbol meaning "the root itself." Just knowing this changes how you see DNS configuration.

Organizing Record Types

While I was at it, I also reorganized my understanding of record types.

You don't need to memorize all of them. In practice, you'll use about 8-10 types.

Commonly Used

Rarely Touched

The description of TXT records as a "catch-all notepad" really clicked for me. Search Console, SPF, DKIM, DMARC, SaaS integrations... it's used for all sorts of purposes.

Why Register Both www and Root

Why do web services register both example.com and www.example.com?

This was another thing I vaguely knew but wasn't clear on.

Historical Background

In the early internet, subdomains were separated by purpose.

www.example.com  → Web
ftp.example.com  → FTP
mail.example.com → Email

www stands for "World Wide Web" and was the subdomain for web servers.

Why www Is Still Used Today

The Correct Pattern in Practice

https://example.com      ← Canonical URL
https://www.example.com  → 301 redirect

The reverse is also fine. The important thing is to "decide on one canonical URL."

From Google's perspective, example.com and www.example.com are treated as separate sites. That's why canonical settings, 301 redirects, and Search Console registration are necessary.

This is actually a crucial point.

DNS Practical Checklist

Finally, I've organized a checklist to avoid DNS accidents.

1. DNS Changes Don't Propagate Instantly

Caches exist worldwide, so changes may not reflect immediately. Be mindful of TTL (300 seconds, 3600 seconds, 86400 seconds, etc.).

2. Make Changes Incrementally

❌ Delete immediately

⭕ Add → Verify → Delete

Add before removing. This is fundamental.

3. Root (@) Is Special

4. TXT Records Accumulate

You can have multiple TXT records. However, SPF needs to be consolidated into a single line.

5. Be Careful with Email-Related Records

Minimum requirements:

Email stops working if DNS is misconfigured, so be cautious.

6. DNS Only Handles Name Resolution

HTTPS, ports, and redirects are not DNS's job.

7. Troubleshooting Commands

dig example.com
dig TXT example.com
nslookup example.com

Use these when in doubt.

8. DNS Is the Last Line of Defense

When DNS goes down, Web, API, email—everything stops.

Summary

DNS is foundational technology that's "boring when you understand it, hell when you don't."

Even after 10 years as an engineer, I forget it because I don't touch it often. The meaning of "@" and the historical context of www were things I vaguely knew but weren't clear on.

I'm glad I could reorganize my knowledge while chatting with ChatGPT this time.

What you need to remember isn't actually that much:

If you keep these in mind, you shouldn't have trouble in practice.