Comment by lucideer | Hacker News Reader

Comment by lucideer | Hacker News Reader

Making 1 request instead of 2 is definitely ideal, so following the recommendations here of using x/api instead of api.x is good advice, if it's low hanging fruit. However, otherwise, is it just me or doesn't this seem like a long tail optimisation?

> If you have a slow network, this could be a huge setback, especially when an OPTIONS request takes 2 seconds to respond, and another 2 for the data.

Firstly if your OPTIONS is taking 2 seconds, CORS is not your bottleneck. Even with a half-second PING due to lack of content distribution, and DNS resolution (shouldn't be an issue after the first request), an OPTIONS request should be of negligible size; the bulk of that 2 seconds isn't going to be network latency, that's a serious server-side perf. issue.

Secondly, similarly, if your OPTIONS is taking equally as long as your GET, CORS isn't your bottleneck.

Yes, considering CORS latency is worthwhile if having your API on the same domain is an easy change, but the title overstates the performance cost.

Once again, the quote is talking about slow network, not the server taking seconds to process an OPTIONS request.

Yes, two seconds and more can absolutely be network latency. If you don't think this is possible nor a regular occurrence for many people, you have been living in a bubble.

> two seconds and more can absolutely be network latency

Not at all contesting this.

> a regular occurrence for many people

Maybe I am living in a bubble, but this seems unlikely unless your definition of "many" is fairly liberal.

On a 2G connection you might get up to 1000ms latency, if you're in a remote part of the world could could add an extra 500ms or more due to geography. DNS lookup, TLS handshake, and the data transfer, you could potentially get up to 3+ seconds adding it all up. But—apart from aspects of that being one-off, as I mentioned above—generally speaking the whole lot is an example of an extreme. Your average user really shouldn't be seeing that.

This assumes good signal. If you have poor mobile signal then you can easily get 5-10 seconds latency.

Are you talking about page-load speeds here or just network latency (the former will obviously be much higher than the latter)?

If the latter, where are you getting 15-10 second figures from?

> this seems unlikely unless your definition of "many" is fairly liberal

In a world with more than 7 billion human beings and a large percentage of them being users of the internet, it doesn’t matter if we are talking about 1% or even only 0.01% of users. Any percentage will include many people.

It might only be many actual users if you’re Google or Facebook, though.

The title of the article is (HN mods have wisely edited it since my initial comment) "The Terrible Performance Cost...", which I'd say implies more impact than the reality.

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