When Optimizations Backfire

JS Nation

I’m attending JSNation – the main JavaScript conference of the year. You may join me there for free with 10k other JS engineers and 40+ great speakers. Just follow this badge. 

#javascript

JSNation 2023

Ivan Akulov

React Performance Debugging Masterclass

React Summit

I am attending the biggest #Reactjs conference remotely. You may get a limited free ticket (50% of talks, no workshops) and join me by clicking this badge.

#react #reactjs

React Summit 2023

React Concurrency, Explained

Get ready for an annual deep dive into the latest trends in React and Web development. Learn from engineers behind the framework ecosystem and early adopters at the main React Conference in the UK.The concept of the event is both about covering all you need to catch up on in the React ecosystem, combined with deep technical exploration of the latest architectural trends, new feature adoption, and efficient ways to solve complex problems.Engage in discussion rooms, hallway track with experts, hands-on practical workshops, and tens of insightful talks. Engineers of any level are welcome but be prepared for hardcore.

React Advanced

React Advanced 2023

React Performance Debugging

React Summit US

React Summit US 2023

React Concurrency × Core Web Vitals

Brace Your React, New Core Web Vitals are Coming

React Day Berlin

React Day Berlin 2023

Invisible Hand of React Performance

React Summit 2024

React Day Berlin 2024

Did you know introducing useEffect solved a whole class of performance issues? Did you know &lt;Suspense&gt; was designed to make hydration several times smoother without you even noticing anything?  React has changed a lot. Many of these changes were driven by a desire for better architecture. But under the hood, each of these changes also pushed us to write faster apps – often, without us even noticing that. In this talk, let’s look at some rarely known React performance details almost nobody knows about: - useEffect, and how it’s faster than componentDidMount- Batching, and how it improved from version 0.4 to 0.12 to 18- Suspense, and some of the less obvious effects of using it- and possibly even more

In a few months, Google will DESTROY your React app......well, kinda. In March, Google is releasing a new Core Web Vital called Interaction to Next Paint (INP). It measures the speed of interactions – and every React site Ivan has seen so far had INP way in red. This is bad for any site that cares about SEO.In this talk, let’s learn how to prepare for the new Core Web Vital: how INP works, and how to improve it – both manually and with new React APIs like useTransition() and React Concurrency.

<div>This talk comes with bad news. Google has launched a new metric – INP – which measures how fast page interactions are. This metric becomes a Core Web Vital in Mar 2024 – and pretty much every React app Ivan has seen so far has this metric way in red.</div><div> </div><div>The good news is React 18 shipped new features that help to solve this – notably, useTransition() and Suspense. And in this talk, we’ll look at how exactly these features work, what they do, and how we can use them to make INP green.</div>

Ivan’s first attempts at performance debugging were chaotic. He would see a slow interaction, try a random optimization, see that it didn't help, and keep trying other optimizations until he found the right one (or gave up). Back then, Ivan didn’t know how to use performance devtools well. He would do a recording in Chrome DevTools or React Profiler, poke around it, try clicking random things, and then close it in frustration a few minutes later. Now, Ivan knows exactly where and what to look for. And in this workshop, Ivan will teach you that too. Here’s how this is going to work. We’ll take a slow app → debug it (using tools like Chrome DevTools, React Profiler, and why-did-you-render) → pinpoint the bottleneck → and then repeat, several times more. We won’t talk about the solutions (in 90% of the cases, it’s just the ol’ regular useMemo() or memo()). But we’ll talk about everything that comes before – and learn how to analyze any React performance problem, step by step. (Note: This workshop is best suited for engineers who are already familiar with how useMemo() and memo() work – but want to get better at using the performance tools around React. Also, we’ll be covering interaction performance, not load speed, so you won’t hear a word about Lighthouse 🤐)

React 18! Concurrent features! You might’ve already tried the new APIs like useTransition, or you might’ve just heard of them. But do you know how React 18 achieves the performance wins it brings with itself? In this talk, let’s peek under the hood of React 18’s performance features: - How React 18 lowers the time your page stays frozen (aka TBT) - What exactly happens in the main thread when you run useTransition() - What’s the catch with the improvements (there’s no free cake!), and why Vue.js and Preact straight refused to ship anything similar

Ever loaded a font from the Google Fonts CDN? Or added the loading=lazy attribute onto an image? These optimizations are recommended all over the web – but, sometimes, they make your app not faster but slower. In this talk, Ivan will show when some common performance optimizations backfire – and what we need to do to avoid that.