From the NordicCDN blog
Performance, caching, security and the craft of running a fast website or webshop.
How to purge your CDN cache (and when you actually should)
Purging is the big red button of CDNs: it clears the cache so changes show up now. Useful, occasionally necessary, and easy to over-use — often as a substitute for fixing the actual problem.
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Why your images belong on a CDN (and what an image CDN adds)
Images are usually the heaviest thing you ship and the easiest big win you are not taking. What a CDN fixes, and the four things an image CDN does that a plain one does not.
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Cache-Control headers: the only guide you'll actually need
Cache-Control decides what gets cached, by whom, and for how long. It looks cryptic and is mostly six words you actually use. Here they are, plus the one distinction that trips everyone.
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ESI explained: cache the page, personalize the bits
The classic caching dilemma: the page is 99% identical for everyone, but that 1% — the username, the cart count — makes the whole thing uncacheable. ESI is one of two ways out, and it is not always the right one.
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Multilingual SEO: hreflang, subfolders and not shooting yourself in the foot
Done right, going multilingual multiplies your search traffic. Done wrong, hreflang gets silently ignored and nobody tells you. Here are the rules and the five ways people break them.
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Cart abandonment and speed: the link nobody talks about
There is a whole industry of advice about cart abandonment — emails, popups, discount codes. Almost none of it mentions the cause that quietly makes every other cause worse.
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How to put a CDN in front of your custom domain, step by step
Putting a CDN in front of your own domain is a short checklist and about four places people trip up. Here is the whole thing in order, including how to undo it.
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TTFB: what a good time to first byte looks like, and how to get there
Time to First Byte is the wait before your server says anything at all, and it sets the ceiling for everything after it. What good looks like, and how to find which part of yours is slow.
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Flash sales and ticket drops: handling 10× traffic gracefully
A flash sale is a traffic spike with a stopwatch on it — and a second problem most scaling advice ignores entirely: there is only so much stock, and everyone wants it at the same instant.
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