It depends on the TTL set on the cached content in CDN. If the TTL is for several hours, CDN won't show the recent content. Given that the TTL is set appropriately for the content, CDN will behave correctly.

Much like DNS, it depends on the TTL. But yeah, if you're trying to do real-time stuff, it's best not to cache that with out-of-the-box stock CDN products, but rather have your own caching. Then for the rest of the endpoints/assets, you can use a default CDN.

Something some people seem to miss though, is to leverage ETag header properly, so the client and CDN can serve fresh content automatically when it exists, or serve the cached content otherwise. It's not that tricky, but somehow many seems to not even know about it.

And the time that you spent waiting to see the logs. They aggreagate them via attached files in mails sended from the pops.

The problem comes down to how quickly configuration data can be pushed to the edge and modern CDNs like Cloudflare and Fastly respond to changes within seconds, or even milliseconds.

Most of the time you change URLs rather than content but it may not apply to real-time scenarios.

Some CDN provides distributed key value stores where you can push data in seconds, you can also deploy your own code in minutes (for real time changes you would push data, not code).

Some providers expose cache purge APIs so you can clear cached data in seconds.

They also allow serving cached content while asynchronously revalidating with the Origin so following users get a fresh version.

With proper configuration/architecture they are a great way to scale your real-time website.

It is changing. I work for a CDN on a team focused on speeding up config propagation. The modern expectation is global distribution of new configs in seconds.

One of the reasons Fastly got used by online newspapers was their fast purge. No newspaper wanted to use CDNs for breaking news if purging took 20 minutes to complete. It was one of the advantages Fastly had that allowed them to get customers from other CDNs. According to https://developer.fastly.com/learning/concepts/purging/ they do single-object purges in 150ms globally.

> It was one of the advantages Fastly had that allowed them to get customers from other CDNs.

That’s a neat fact and perhaps an advantage usually reserved for new entrants into an entrenched market. Presumably Fastly benefited, at least in some part, from technological innovation that existing companies could not apply as easily.