Is Performance Always Important?

Question

Since I am a Lone Developer, I have to think about every aspect of the systems I am working on. Lately I've been thinking about performance of my two websites, and ways to improve it. Sites like StackOverflow proclaim, "performance is a feature." However, "premature optimization is the root of all evil," and none of my customers have complained yet about the sites' performance.

My question is, is performance always important? Should performance always be a feature?

Note: I don't think this question is the same as this one, as that poster is asking when to consider performance and I am asking if the answer to that question is always, and if so, why. I also don't think this question should be CW, as I believe there is an answer and reasoning for that answer.

Answer 1

Adequate performance is always important.

Absolute fastest possible performance is almost never important.

It's always worth keeping an eye on performance and being aware of anything outrageously non-optimal that you're doing (particularly at a design/architecture level) but that's not the same as micro-optimising every line of code.

Answer 2

Performance != Optimization.

Performance is a feature indeed, but premature optimization will cost you time and will not yield the same result as when you optimize the parts that need optimization. And you can't really know which parts need optimization until you can actually profile something.

Performance is the feature that your clients will not tell you about if it's missing, unless it's really painfully slow and they're forced to use your product. Existing customers may report it in the end, but new customers will simply not bother if the performance is required.

You need to know what performance you need, and formulate it as a requirement. Then, you have to meet your own requirement.