Book by Tammy Everts published in 2015
Good book on performance. Likely the best compromise between pragmatism and data so far. That said, the data feels weak.
When things are slow, people get anxious. Think about how uncomfortable it is when it's taking 20 seconds for your airline ticket transaction to go through, or 10 minutes for the confirmation email. The book really drives this home. It's not just that people will click more and faster, it's also that it creates this feeling of stress that it's hard to shake.
One of the more interesting things mentioned I hadn't heard before is that 100ms is about the time we hold on to an image. If something's faster than that, we see motion. Take a piece of fiery coal and spin it around. If the cycle takes less than 100ms, we see a glowing red circle. Pretty. If it takes more than that, it's not going to look as nice.
An interesting point that Tammy gets through is that we focus on downtime as a conversion killer. But really, bad performance is a slow killer that often outranks it because it's active much more of the time. Akamai had some study (again, I hesitate to cite because there's not much scientific rigour here) that a site being down causes a permanent abandonment rate of 9%. Slow performance, 28%. Now, this illustrates well my ambivalent frustration throughout the book: That's some amazing data. Love those numbers. But I can't share them, because it's not clear what they mean. What's "slow" here? Seconds? Or hundreds of milliseconds? Over what time period? How long was the outage? Ugh. But too much flash. This, along, brings it down two stars.
Something I quite liked is that humans really just prefer things that are fast. We don't have a super good understanding of why. So, someone did a test of a site that took 100-200ms and one that took more than 500ms per page load and asked people to use some adjectives. When websites are slow, they'll say things like "boring", "inelegant", "clunky", "tacky", and "hard to navigate." That's pretty cool. I relate to it like this: These are all words I'd use to describe Word last time I tried it. I assume the codebase is a travesty. I don't really know, I've just sort of decided that because it hangs too much. If it had been flying fast, I might assume this is a rock-solid piece of engineering. You get some more leeway. Of course, you can have one of those 2nd tier Italian cars that are really fast, look really good, but break down all the time.
Also. Seems like people in Australia are more patient about latency than in the US. That's pretty interesting. Coping mechanism with Pacific latency.