Author here. CloudFlare's DNS was measurably, and consistently, faster than almost every provider we tested. So I can concur with you in that regards. It was ultimately faster than Route 53 and Google Cloud (the path we ended up going).

However, when our relationship with CloudFlare ended and we moved to Fastly, one of the reasons we did so was unreliable lag with DNS updates at CloudFlare. Sometimes it would take minutes or hours for DNS changes to be affected in their system, and they could never provide a satisfactory reason why.

+1 - I am also very interested why they chose to switch out from CloudFlare for both their DNS and their CDN and over to Fastly. Nick Craver did a write up where they specifically mentioned [1] Cloudflare for both their DNS and CDN.

Do you think after the Dyn outage everyones sysadmins are running round adding redundancy, too worried to trust the uptime of their site in the hands of just CloudFlare?

[1] http://nickcraver.com/blog/2016/02/17/stack-overflow-the-arc...

The fact that they abandoned Cloudflare only 6 months after this post means that they must've been pretty disappointed. I wonder if this is the same reason as for some of the other pages that went to Fastly from Cloudflare (e.g. Imgur).

It could also be due to some mundane detail like the service's cost.

He mentioned 503 errors and "missed deadlines". I don't think it's costs, they were known beforehand, you wouldn't switch after 6 months because of costs. And I think if you're at that scale, you'd get a counteroffer from Cloudflare if you threaten to leave.

As you can whitelist Tor traffic in Cloudflare, it seems to be down to these 503 errors (edge to origin). But haven't heard that before, so not sure if it's a problem that occurs more often.

For Imgur, I could imagine that purging by cache tag is just too restrictive at Cloudflare (the limit is very low, even for Enterprise clients). Fastly doesn't have a limit there, they encourage you to cache everything and purge where needed. Makes it much easier to cache APIs and HTML pages.

tl;dr: Javascript/Google reCaptcha Paywall.

Source:

https://meta.stackoverflow.com/questions/323537/cloudflare-i...

They have a DNS service which can be used independently of their caching.

I came to say the same thing. I use Cloudflare as a DNS provider for my own site as I was impressed by the numbers. It's literally as straightforward as clicking a button to prevent Cloudflare from proxying traffic to use their service only for nameservers.

Pretty sure the captcha can be switched off for enterprise clients (which I presume SO would be).

Regarding caching, SO's caching is extremely aggressive. It's especially problematic when editing answers more than once, because when you click edit you'll be presented with a cached copy of your answer, potentially excluding your latest revisions. So you have to refresh the edit page and then edit the answer.

It might seem like an edge case, and it certainly teaches you to be meticulous about answering lest you have to go through the refresh hell, but it's not what some would designate as 'good UX'.

I am never surprised by SO's reports about how they run their busy website from a mere handful of machines precisely because of the caching they do.

Can't believe they're running on Windows. Yikes.

One major issue with their dns was unpredictable lag while changing records. On most occasions we can change a record and it would propigate immediately. In some rare cases, it could take fifteen minutes, and in a few instances up to eight hours before the change would show up on their nameservers.

Cloudflare was unable to diagnose this or give us any comfort that it would improve.