Imagine you visit a site and request the same image your friend just opened. Without caching, the origin server sends that image all the way to you again from scratch. A CDN changes that part.<\/p>\n
First time someone requests a file, the CDN checks if it already has a stored copy. If not, the request travels back to the origin server, CDN gets the file, stores it at a nearby edge location, sends it to the visitor.<\/p>\n
After that first request, things get easier. Someone else in the same region asks for the same file, CDN checks its cache before bothering the origin server. File’s there and still fresh, CDN sends it directly.<\/p>\n
That’s a cache hit. The origin server doesn’t handle that request again at all.<\/p>\n
Because the copy’s sitting closer to the visitor, the file travels a shorter distance. Pages feel quicker, you just stop thinking about why.<\/p>\n
Two basic outcomes when the CDN gets a request. A cache hit means the content’s already at the edge, ready to go. A cache miss sends the CDN back to the origin server, takes longer that first time around. Fresh content stays available until its cache rules say otherwise, exact period depends on how the site’s configured.<\/p>\n
Cache hits are really where a CDN earns its keep. A busy site might get thousands of requests for the same CSS file or product image, serving those from the edge keeps the origin from doing the same job over and over.<\/p>\n
Doesn’t live at the edge forever. Sites set rules for how long different content stays fresh, usually controlled through cache settings and HTTP headers.<\/p>\n
A logo might stay cached a long while since it rarely changes. A page showing changing info needs a different approach entirely.<\/p>\n
So the CDN checks freshness before serving anything. Copy’s expired, it goes back to the origin for a newer version.<\/p>\n
This is where it gets interesting. Update an image on your site, visitors might still see the old version if it’s sitting in CDN caches somewhere.<\/p>\n
Fix is usually cache invalidation, often called purging. You tell the CDN to remove the old copy, next request fetches the updated file from the origin and stores that newer version instead.<\/p>\n
Biggest benefit’s simple, the origin server has way less work to do. Instead of every visitor reaching back to the same server for every static file, the CDN handles a ton of requests from its edge locations. Reduces pressure on the origin, makes popular content easier to deliver during traffic spikes.<\/p>\n
Images and static files are usually perfect cache candidates, especially ones that don’t change every few minutes. Dynamic pages need more care though, serving an old response there creates a genuinely annoying problem. A well-set cache policy feels invisible, which is exactly how good caching should work.<\/p>\n
Caching’s honestly one of those things you notice most when it’s set up badly. A stale image looks off, a slow page feels broken. But when a CDN gets it right, content just appears when you expect it to.<\/p>","protected":false},"excerpt":{"rendered":"
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