Performance Matters More Than You Think

It’s easy to dismiss performance work as premature optimization. And sometimes it is. But I’ve found that in practice, performance problems tend to sneak up on you, and by the time they’re obvious, they’re expensive to fix.

Death by a thousand milliseconds

Rarely does a single change tank your application’s performance. Instead, it’s a gradual accumulation: an extra database query here, an unoptimized serialization there, a component that re-renders when it doesn’t need to. Each one is trivial in isolation. Together, they create an experience that feels sluggish.

The best defense is a culture that treats performance as a feature, not an afterthought. That means measuring from the start and setting budgets before you need them.

Measure what matters

Not all performance metrics are created equal. A fast server response time doesn’t matter much if the client takes three seconds to render the result. I’ve learned to focus on metrics that reflect what the user actually experiences:

Time to interactive — when can the user actually do something?
Perceived latency — does the interface feel responsive?
Tail latency — what happens for the slowest 1% of requests?

That last one is especially important. Averages hide problems. A p50 of 100ms and a p99 of 5 seconds means one in a hundred users is having a terrible experience.

Simple wins

Some of the most impactful performance work I’ve done has been surprisingly straightforward:

Adding an index to a database query that was doing a full table scan
Implementing pagination instead of loading entire datasets
Caching responses that rarely change
Lazy-loading components that aren’t visible on initial render

None of these required a PhD in systems engineering. They just required paying attention to where time was actually being spent.

The compound effect

Performance improvements compound in ways that aren’t immediately obvious. A faster API response means fewer timed-out requests, which means fewer retries, which means less load on your servers, which means more headroom for growth. It’s a virtuous cycle that starts with caring enough to measure.