Performance, Analytics

Wilson Mendes


Google Developer Expert Web technologies

Frontend apps

 and Reliability in  your 


How long is 2 seconds?

Speed feedback

Speed metrics


~1.2 seconds

~1.4 seconds

How about 5G ?

A real picture of internet in the world

How faster is that?

Download speeds for anywhere from 100 Mb to 10Gbit per second. 5G is expected to be as much as 10-100 times faster than 4G. Plus: 4G gets improved as a side effect as well

Downloading 1 episode of Game of Thrones within 90 sec (4K) or 35 sec (1080p), or fetching the entire season in 15 mins (4K)

Measuring Performance

A real picture of internet in the world

Step 1: Define baselines

Page load errors

📈 Real user Monitoring

Async load components

Critical path management

Optimistic preloading

Setting performance budget

What else?

What if we missed 


Bundle size feedback

Comments in pull requests Priority for main bundles

Proactive actions

Performance priorization



Web Vitals

Core Web Vitals

Core Web Vitals

Core Web Vitals

Core Web Vitals

Which metric is the

best for my app ?

Not sure ?

Just don't measure technology


👑 King 👑

User experience

is the

Step 2: Define architecture



POST /v1/metrics








Chaos scenario

What if your

API goes down?

What if your

API have

optional attributes?

What if your

types are not


// GET api/endpoint/1234

  "location": [...],
type ApiEndpointResponse = {
  location?: Array<...>;
  listing?: {
    [k: string]: | string
                 | boolean
                 | number;
// GET api/endpoint/1234

  "location": [...],
  "listing": {...}

Let's create some Chaos

... before production, of course!

“Chaos Engineering doesn’t cause problems, it just reveals them”

Nora Jones, Chaos Engineering Lead Slack

Chaos engineering

Plan it, plan it, plan it!

Prove your hypothesy

Define boundaries for your case

Tooling for chaos

Alerts & monitoring

Always alert

Working proactively in caveats

User conversion for real

A/B test measurements

A/B Test

User Timing API

...because you user measurements can get even better

Marks and measures

Perf-marks in action

Next steps

... or "Measurements will drive ... ?"

Faster UX by ... design?

Perf-Marks NPM package



Web Perf - cases & experiments



Web.Dev - Performance

Thank you  👋

Wilson Mendes


Google Developer Expert Web technologies

Performance, Analytics and Reliability in Frontend Apps

By willmendesneto

Performance, Analytics and Reliability in Frontend Apps

Are you working with a large frontend application and you are facing problems in your project? Problems like memory leaks and performance bottlenecks can be real issues in your site and there are some of the features there are really useful to improve the performance of your web app… but what if it’s not enough? How to combine performance validation between backend and frontend via instrumentation, analyzing and improving the reliability of your web app by user journey improvements? What if you want to track a specific feature in your code? In this talk, I will share my experience and decisions creating frontend components and applications focused on performance, how to manage quality, monitoring, and other techniques that will make your application more than just fast, but reliable for your users!

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