Domain, DNS, Hosting, and CDN

Build the mental model

A domain (example.com) is a human-readable address; a subdomain (learn.example.com) is a labeled subsection of it. The part like .com is the TLD. Owning a domain does not mean you have hosting.

A registrar is the company you buy and manage a domain through. Note that the registrar, DNS provider, and host can be separate companies.

DNS maps a domain name to a destination - keep the mental model domain -> DNS -> hosting. Record types (A, CNAME) exist, but their administration lives in Cloud & Deployment.

Static hosting - simple, unchanging files
Shared hosting - resources shared across many sites
VPS - your own virtual server
Cloud platform - scalable, managed infrastructure
Serverless - function-level, on-demand execution
Container - a packaged, portable environment
Managed platform - the hosting company handles the operations

A CDN caches content across many geographic locations and serves users from the nearest one, reducing latency and origin load.

Domain: A human-readable name (like example.com) used instead of a numeric address to identify a site on the internet.

DNS: The system that maps human-readable domain names to the addresses or destinations they should point to.

CDN: A distributed network of servers that caches content in multiple geographic locations to reduce latency and load on the origin server.

text

DOMAIN, DNS, HOSTING, AND CDN
-----------------------------
DOMAIN, DNS, HOSTING, AND CDN
-------------------------------

  learn.example.com
        |
        v
  [ DNS ]  -- resolves the name to an address
        |
        v
  [ Hosting / Origin Server ]

CDN EDGE CACHING
------------------

              +----------------+
              |  Origin Server |
              +----------------+
                      |
           distributes cached copies to edges
                      |
     ------------------------------------------
     |               |                        |
 [CDN: US East]  [CDN: Europe]           [CDN: Asia]
     |               |                        |
  User (near)     User (near)             User (near)

Connect it to a real scenario

A concrete flow: buy the domain, point DNS at hosting, serve static assets from a CDN, and send dynamic requests to the origin.

The code below looks at a request's description and decides which of DNS, CDN, or Origin Server would typically handle it.

Domain, registrar, DNS, and hosting are four distinct roles that can be run by four different companies.
DNS maps a domain name to a destination; hosting is where the code actually runs - a domain alone doesn't mean a site exists yet.
A CDN serves cached content from locations near the user, reducing latency without changing where the origin server lives.

Try the working example

javascript

function routeRequest(request) {
  if (request.isFirstDnsLookup) {
    return "DNS";
  }
  if (request.isStaticAsset) {
    return "CDN";
  }
  return "Origin Server";
}

const examples = [
  { label: "First visit, resolving learn.example.com", isFirstDnsLookup: true },
  { label: "Loading a cached logo.png", isStaticAsset: true },
  { label: "Fetching /api/dashboard for a logged-in user", isStaticAsset: false },
];

examples.forEach((ex) => {
  console.log(ex.label, "->", routeRequest(ex));
});

You should see

Logs three routing decisions: the first-visit lookup routes to 'DNS', the cached image routes to 'CDN', and the dashboard API call routes to 'Origin Server'.

5-minute try-it

Look up which company registered a domain you use, and separately check which company appears to be hosting or serving its static assets (a browser's network panel or a DNS lookup tool can reveal both).

One important caution

Assuming buying a domain automatically means a website is live somewhere - a domain is just a name, not hosting.

Treating registrar, DNS provider, and host as always being the same company - they often are for convenience, but architecturally they're separate roles.

Wikipedia - Domain Name System — How the Web Works