Houssein Djirdeh

Performance Empathy

Performance advocates spend a lot of time telling developers how to build fast and reliable experiences on the web. Every website is built differently, however.

Instead of just listing a number of progressive enhancements and techniques, this talk will try to take a different approach. We’ll first explore who needs to consider improving their site in the first place and see if their is a messaging problem between advocates and developers in the community. We’ll then address concerns that can arise when performance is being worked on and discuss some real and practical solutions.

Portrait photo of Houssein Djirdeh


Yeah, as Aga mentioned, my name is Houssein, and I will be talking today about performance empathy. Empathy's a term we commonly use to describe the ability to understand and share the feelings of another individual or a group. I like to think of the term "performance empathy" to be the same thing, but for the performance concerns and issues of a particular site. To explain why I thought it would be a good topic for a talk, I need first to describe a bit more about myself.

I work as an advocate for the web team at Google. Now, developer-advocates in many different companies usually act as a bridge between a specific engineering community and a specific engineering team and a developer community.

Being an advocate for the web team means that it's my job to make sure the web gets better and better. I focus on speed and performance. So a lot of advocates, we sometimes give advice that can seem a little overwhelming. I don't know why my clicker feels weird! There you go. [Scattered laughter].

But in all seriousness why are so many performance advocates fascinated about what they do with their own tool chains? Why are we so focused whether it will improve performance or not? Why do we care performance that much to begin with? Is it really that much of a problem? To help us answer this question, let's look at this example of a site. It's an entirely client-side rendered site that ships a megabyte of JavaScript. This means that the initial request only contains a shell of an HTML document. Only after the JavaScript bundle finishes executing, the user gets to see any real content.

Now, in case you weren't counting, the amount of time it took for this app to finish loading was about 19 seconds. 19 seconds isn't fast by any means.

So we know that one megabyte of JavaScript can seem like a lot to ship town to browsers. How much are we generally shipping? If we take a look at the HTTP archive, we can see the median amount of JavaScript we are sending down the wire is about 350 kilobytes, and this for mobile web pages. The reason this is such a big deal is because a lot of websites currently living in the web that are either entirely static or they have little to no interactivity at all. I thought it would be interesting to dive in a little deeper and see how much how much site they use of a particular framework are shipping in terms of JavaScript.

And I did it with three frameworks to begin with: Angular, React, and Vue. The reason I chose these three is because they are the most popular client-side frameworks today to build our UI. I found out after querying 250,000 origins, about 50 per cent of them ship over a megabyte of JavaScript. Now, each of these origins either use one or more of these frameworks.

There's a lot of reasons why this might be the case, but it does show that we are shipping a lot of JavaScript if we are not entirely careful. Now, what I want to do now is take a step back and talk about how I began the presentation.

You see, every single talk I've ever given before today has always followed the exact same format: I begin with a word of caution, and talk about how performance is a pretty big problem. I then move on to showing some stats and some numbers to back up my claim, and I do this to convey how much of a problem this actually is. And then the rest of my talk usually follows the same sort of pattern where I talk about different tips, different techniques, that you should be applying to make sure your site stays as small as possible and as fast as possible. For this talk, I'm going to go in a slightly different direction.

I want to talk about what we can do as advocates, and what we can do better to reach the community better, as well as how we can all work together to try and think of different ways to to make sure performance is a win for everybody. Going back to that example of a site we just talked about, here I mentioned that, at the end, I mentioned that we are running this on a mobile device and a slow 3G connection. A lot of people when they trace performance, they talk about specific user conditions that might not be the same as yours when you build your application. And we do this because the fending on the user's device or network type, they can experience your site a lot slower than you think. And there's more.

We sometimes talk about how your users might experience your site if they're completely offline, or if they have a flaky network connection, or maybe they have a weaker device, on mobile, so forth, and so on. Although it is important to talk about all these scenarios and try to capture different conditions your user might be in, the thing I want to make sure I mention is that you know your users better than anyone else. You definitely know your users better than any advocate that stands on stage telling you how well your site performs under a certain condition. That being said, one thing I want also to mention is the fact that nobody prioritises performance over anything.

If you think about it, when you're trying to build a site, the very first thing you're thinking about usually isn't performance. Most people are like this. But if you also think about it, why should someone make it the very top thing they think about? Let's talk about something to try and complain what I mean here. Say you wake up one Monday morning and you have an amazing idea.

You've thought about a product you want to sell on the website or maybe you want to provide a specific type of service. So you're excited, and the next thing you naturally do is try to find out how to build it.

You spend a little time researching the tools, the tips, the tricks that you need, maybe you're building wire frames, maybe building graphics, so forth and so on, but only after that, you actually start building. And at this point, throughout the initial process, nobody really thinks about performance. The thing that you actually most likely are thinking about is the fact that you want to build a site that loads and does exactly what you expect it to do, but build it with as minimal effort and as fast as possible. A second possible scenario could be the fact that you join a brand new team as a developer. Say the newest developer on a brand new team, and, when you get assigned your first ticket, you're most likely going to try and familiarise yourself with the code base.

You will spend a little time trying to know where your components live, where the utilities live, how the unit tests work, and so on. Only after that, while you're doing that, you start building and working on your first feature. Maybe it's a small feature you're adding on a page, maybe it's a small bug that you're working on. But again, also, when you're in these shoes, you're not thinking about performance. You're not think about what I'm building doesn't degrade the performance of my site.

No, it's the first thing you're doing, most likely trying to check every single box assigned to you. It's highly unlikely performance is on that list. The way I like to think about awareness and performance in general, and how people are aware of the performance and location of the site, I try to think of it as some sort of scale. For example, let's say you're building something for the first time, or you're building something for the umpteenth time which you're learning a brand new tool.

What you're going to be doing at this point is seeing how this tool works. Does it do what you expect it to do? You're going to learn the API, is it easy to plug into your site? At this point, it's unlikely you're unlikely thinking how badly it's going to affect your performance. You're thinking how easy is it for me to use? Let me spend some more time with that, and after a while, you end up launching your first website. You have an idea of how it works in development mode and how it works in production mode.

You have a better feeling whether it is really affecting performance or not, but you still might be slightly unsure of what you need to do about it. But the more and more you use this tool, and the more websites that you build, the more familiar you are with how it affects the speed and reliability of your site.

That being said, nobody is more aware with the fact that they need to work on performance than those that actually know they have issues. If a significant per cent of your user base tells you we can't access your site because it's too slow, you're most likely going to try and prioritise it as soon as possible. This is what I mean by performance being an afterthought. Maybe there are ways out there of it being not of something we only think of when it is too late.

Throughout this talk, I sort of this this dichotomy between two different users groups, one being performance advocates like myself, and one being a normal developer working on a regular codebase. Now, advocates, I think we all agree on the fact that there are way too many slow sites, and the reason why I think this is true is because we have our job because a lot of the sites out there aren't as fast as they should be. If every user accesses the website and felt like it was faster than it needed to be, we wouldn't need to be doing what we do every day. But there's another misconception, or another thought that sometimes gets misconstrued that seems kind of weird, and it's the idea that developers are sloppy when they ship slow experience. I've seen the sentiment time to time, and I can't understand it, because a developer working on a website, and it happens too bad too slow, it is usually one of three reasons.

One, they don't know it is too slow for their users, two, they know it's too slow but they don't know how to fix it, or they haven't prioritised that yet, and, three, they know it's too slow and they're actively working to effectively. Indeed again is always relative. Having an advocate tell you that you're not focusing on something very important to them isn't always the best approach.

Now, on the other side of the coin, when we talk about a developer, when you're building a website, you're most likely going to agree that you have a million things you can work on. Performance is just one of them. But it's also another weird thought that I see sometimes floating around and it's the idea that advocates, or performance advocates, specifically, are out of touch. The reason why some people might think this is because of the fact that many performance advocates will build small sample apps and show you how to optimise and some people will feel it's not easy to do it with a massive codebase and a massive team where code is being checked in everywhere.

The reason why I want to squash this thought is because advocates have been in your shoes. We are developers.

We worked with teams who understand that there are more concerns to a site than there is just performance. Instead of having the back-and-forth between small weird opinions and small, small thoughts, I think it's safe to say we all agree towards one common goal: we all want the web to be faster for everybody. So the big question is: how can we make sure we can fix the performance problem better? What I'm going to do is talk about a few ways we can explore that, because there are changing sort of how we think about making things better for our developers. The very first is making sure everybody has better defaults. What I mean by default is the idea is that let's say you're building something with a certain tool.

If it always gives you a better starting point, you will most likely always have more wiggle room, and more room to play with where it will take you longer to reach a threshold or performance and end up being slow. And in terms of framework level, a lot of frameworks are looking into this already. React has already been looking to try to improve React DOM and make the sites smaller. Doing this a few different ways, one of them being simplifying its event system. With Vue and Vue3, they are looking to reduce memory function and making things more tree-shakeable where they can.

The Angular team is looking into building brand new rendering engine called Ivy, and with it exploring ways to cut down the initial bundle size and also looking at ways of maybe progressively heightening experiences when you have server render architectures. React and Suspense is also doing the same thing. And then there are metaframeworks, things like Next.js that allow you to do what you want to do most of the time, write and build your component. There are things that we tell people to do quite often.

You should be code - these frameworks take it out of the hands of the develop. Developer. We are already working with XJS to see if we can do things even better and even have smaller bundle sizes and make sure users get the best experience wherever they can. When we talk about defaults, the only way to think about it too is the default APIs or the out-the-box APIs that the browser provides.

It will be a lot easier if we didn't have to leverage third-party libraries or write scripts ourselves when we try to optimise things that the browser can probably do already. An example of this is the lazy-loading attribute.

Now, if anybody here is actually building something with a lot of images, you most likely realise that having a lot of images load at once can affect performance, so people have become quite used to either pulling in a third-party library or writing their own custom script that takes advantage of the intersection observer API or scroll-event listers to only add listers to those close enough to them. The loading attribute is something that will be rolled out to Chrome pretty soon, and by using it with any image or iFrame tag, it will automatically lazy-load images after it reaches a certain distance threshold from the bottom of the viewport. Think about the wins this can make to any developer. Think about the main developers that don't know how to build their own lazy-loading scripts or even know if there is such a thing, but once they realise there is a simple app they can add, it will make it a lot simpler for everybody.

Another example of an API that makes things easier is the virtual scrolling API that is also being worked on right now. If you've ever built anything, a site with a long table, or very large list, you also realise that having all those DOM nodes populate at once can affect rendering performance. And the idea behind this virtualisation or virtual scrolling is to make sure that only the nodes or only the items on the list that the user can see is populated through DOM, and as the user scrolls down, those DOM nodes get recycled with newer DOM nodes. A lot of frameworks like React, like Angular, have third-party libraries that allow you a virtualised list. Having a bake-in API means you can do this without relying on any of them at all at all.

For example, accessibility concerns, or the find on page feature, or how could SDO crawl your page, or a crawler crawl your page, and detect things that are not rendered to the DOM just yet? Another very important thing we also realise is in general, we need better guardrails for all developers. We've noticed a pattern where we tell people to optimise, and a lot of teams will go ahead and they will start doing so. After a certain period of time, feature creep is in, new code is being shipped, or they regress to the initial state or the state worse than prior. The idea behind guardrails is what if you had something that made sure everybody stayed accountable and made sure everybody stayed on a narrow path? One such example of a guardrail is a performance budget.

A performance budget is a budget for certain performance metrics that you make sure your app never exceeds. There are many tools out there that can allow you to add performance budgets. One such example of those recently launched was something called Lighthouse, a team built by the Chrome team that allows you to audit how well your pages are doing. It allows to check for accessibility, performance, and so on.

A lot of developers use Lighthouse every day in their work flow, and the idea is what if you can specify a single JSON file to add performance budgets into it? You can specify different resource types, define the budget that you never exceed, as well as the defined third-party request and make sure the number of requests never exceeds a certain value. The third most important point, and I think this is something that actually resonates with me quite well, is the fact that we need to meet develops where they are.

As an advocate, if we are telling developers that they need to change their entire work flow, or the tools that they're using isn't going to work and they have to swap it out for another, we're not going to go very far. And it's something I've seen more and more of right now. What I'm trying to do is trying to improve the fact that whatever tool you decide to use, whatever framework or library you decide to use, what if we could always make sure that tools stays and performant as it possibly can? And in terms of how we are trying to do this one way is through tooling. And there is a feature called Stack Back. This extends to Lighthouse but in a different way.

The idea behind Stack Pack is that it allows Lighthouse to detect what tools are being run on your page and then give specific recommendations specific to that room. Let's say you're using WordPress to build a site, and you're working out how to properly side your images. You can read a highly generalised advice that will apply to anyone, but see advice that is more specific to you. You see how to do it using the WordPress. The idea with Stack Pack, we try to roll this out to many Java frameworks and CMS tools.

WordPress is the only one that is supported right now. Documentation is always going to be a big deal, and it's going to be a big deal for a while. Now, in Google and the Chrome team, we have a lot of documentation at a high level, generalised, and they work for the main developers as they possibly can. They're trying to roll out frameworks-specific guidance.

This is a new documentation site that we have that is more interactive and specific to the user, and recently launched a whole section on frameworks. The idea is we're not - the idea is we're not trying to teach you how to use a tool like React, we are trying to show you how you can make your React app as fast as possible using in-built React APIs and third-party libraries in the React ecosystem. We plan on having more Angular View and other frameworks in the future. In the Chrome team we've also been doing in terms of monitoring support.

Malte and Nicole announced this and mentioned something called framework fund. A lot of people working in open source, a lot of developers in open source, and how can we support them in more than one way, to continue to try to increase performance of their tools or those who use them will get better defaults, better guardrails, and more.

When it comes to fixing the performance problem, I think as advocates, we are doing it in two sort of ways, one being which I call internal support. We write blogs to tell you how to do things. We build third-party libraries that you can plug in through sites. We give talks at a place like JSConf and tell you what you need to do to improve the speed your site.

Then the internal side of things. How does the tool you're using get better by default? What if they get better at a starting point? What if they have better guidance and better warnings? As of now, I currently feel we're more so on the external side, and that's fine. We will continue to do that as long as we can reach more developers can we possibly can. What I would like to see in the next few years is a shift in the other direction. In an ideal world, we wouldn't have to tell developers what to do if every tool they're using already does it automatically.

I hope you enjoyed this talk as much as I enjoyed giving it. Thank you. [Applause].