Article based on the talk by Alejo Fonseca & Juand Londoño presented at Open Tech 2025 on Saturday, September 6, 2025.

Summary

Website speed is not a technical detail—it’s a critical business factor that affects conversion, retention, Google visibility, and user trust. In their Open Tech 2025 talk, Alejo Fonseca and Juan Londoño walked through a step-by-step approach to improving web performance using Core Web Vitals, CDN and edge strategies, server-side rendering, image CDNs, and frontend best practices. Through a real case using Spartacus, they demonstrated how they improved performance from 40% to over 90%—without backend access—and reflected on the strategic role of speed in today’s digital ecosystem.

When a Millisecond Is Worth Money

In the physical world, if a store door doesn’t open, you try again.
Online, that never happens.

If a page doesn’t load within a couple of seconds, users close the tab and move on.

No anger, no complaint—just competitors two clicks away.

That was the idea Alejo Fonseca and Juan Londoño used to open their talk at Open Tech 2025:

“Web performance isn’t a technical issue—it’s a business issue.”

Every second (or fraction of a second) translates into lost users, abandoned carts, mistrust, and revenue loss.

As they put it—with surgical clarity:

“A slow store loses sales, retains fewer customers, and slows its own growth. It doesn’t matter how good your product is. If your page doesn’t load, your business doesn’t work.”

From TikTok to Your Ecommerce: Modern User Expectations

Users no longer compare your site to competitors in your industry.

They compare it to Instagram, TikTok, and YouTube.

Apps that load in milliseconds, never freeze, never hesitate.

That’s the mental benchmark.

No one thinks:
“Well, this ecommerce must be slower because it sells mattresses.”

If the page lags, the user abandons and finds another option.

As highlighted in the talk:

• A 1-second delay can drastically reduce conversion.

• Large companies lose millions to slow performance.

• Small businesses can stagnate from not optimizing.

In simple terms:

Speed is no longer a nice-to-have; it’s an essential part of the product.

Google as Judge and Player: Core Web Vitals

Google observed user behavior and turned it into concrete metrics: Core Web Vitals—the holy trinity of web performance.

Alejo and JP explained them in simple, human terms:

• LCP (Largest Contentful Paint)

How long it takes for the main content to appear.
If nothing shows up, the user feels like nothing is happening.

• CLS (Cumulative Layout Shift)

How much the layout “jumps” during loading.
That annoying moment when the button moves just as you try to click it.

• INP (Interaction to Next Paint)

How fast the page responds to user interaction.
If the user clicks and nothing happens, it’s game over.

These metrics not only measure quality—they directly impact SEO.

Google simply shows slow pages less.

As the speakers said:

“No matter how much marketing you put behind a site, if it’s slow, it won’t be seen.”

The Magic Equation: Performance + Experience + Trust = Conversion

A fast page:

• communicates professionalism

• builds trust

• encourages word-of-mouth

• increases sales

• reduces abandonment

And the impact is measurable.

Amazon found that 100 ms can equal 1% fewer sales.

Google reported that 0.5 seconds faster can increase traffic by 20%.

Few technical factors have such a direct impact on profitability.

How Do You Know If Your Page Is Fast? Essential Tools

The speakers highlighted two key tools:

• Lighthouse

• WebPageTest

 

They audit and identify performance issues like unnecessary JavaScript, heavy images, server issues, lack of caching. And Lighthouse is precisely where the practical case began.

Real Case: Improving Spartacus Without Touching the Backend

For the demo, they used Spartacus—well-known to the Pyxis team.

The initial Lighthouse audit showed:

• Performance: 43%

• Accessibility: good

• Best practices: acceptable

• SEO: low

All this using only the public backend—no internal optimizations allowed.

The goal: push performance above 90%.

Did they make it?
Yes.
Was it easy?
Not at all.

Step 1: Getting the Frontend “In Shape”

Before applying advanced techniques, the foundation needed strengthening:

•  Lazy loading

Load only what the user needs, when they need it.

• Bundle reduction

Shrink JavaScript size:
fewer heavy libraries, dead code elimination, more efficiency.

• Stable rendering

Avoid layout shifts by defining width and height for images and containers.
This significantly improves CLS.

• Internal code cleanup

Good practices, subscription control, modern HTML, removing unnecessary dependencies.

This “carpentry work,” as Alejo and JP called it, is what allows more advanced improvements later.

Step 2: Optimizing Infrastructure (The Big Leap)

A page doesn’t rely only on its code.
Infrastructure plays a huge role.

1. CDN (Content Delivery Network)

A global distributed network that sends content from the server closest to the user.

Concrete benefits:

• lower latency

• better availability

• faster pages

• reduced load on the main server

• built-in failover

If you have users in multiple countries, a CDN is mandatory.

2. Edge Computing

The “middle layer” between server and user.

It allows:

• smart caching

• immediate responses without hitting the backend

• fine-grained rules: what caches, for how long, what bypasses

 

This alone improved performance by about 20 points.

3. Vercel / Firebase Hosting + Client-Side Rendering

Deploying the frontend on performance-optimized networks adds several speed points.

This stage took Spartacus from 43% to roughly 80–85%.

Still not enough.

4. Server-Side Rendering (SSR)

This was the game changer.

Rendering the page on the server and sending it pre-built dramatically speeds up perceived load.

Benefits:

• content visible much faster

• better SEO

• better performance on low-power devices

SSR makes performance hardware-independent.

5. Image CDN (Cloudimage)

The star of the show.

A specialized image CDN:

• compresses automatically

• switches formats

• resizes

• serves optimal images per device

• caches intelligently

As they put it:

“An ecommerce is basically a page full of images. Optimizing them means optimizing everything.”

This is what finally pushed performance past 90%.

Final Result: 93% Performance (Without Touching the Backend)

Final scores:

• Performance: 93%

• Accessibility: 100%

• Best practices: excellent

• SEO: 92%

It could have been even higher with backend control.

The goal wasn’t 100%.

The last 6–7% comes with disproportionate cost and minimal real benefit.
Even Apple sits around 89%.

Perfection rarely pays off.

Audience Questions: Caching, Browsers, and the Myth of 100%

Key takeaways from the Q&A:

Can you cache “everything”?

No.
The cart, for example, must remain dynamic.

Can a slow backend ruin everything?

Yes.
That was the main ceiling in this case.

Chrome vs. Safari vs. Firefox?

Differences exist, but Lighthouse and PageSpeed provide balanced measurement.

Is 99% possible?

Yes—but it’s not worth it for most businesses.
The complexity outweighs the marginal gain.

Final Message: Performance Is Part of the Product

Optimizing performance is not “making the page load faster.”

It is a business strategy affecting:

• sales

• branding

• user perception

• retention

• SEO

• trust

• overall experience

As Alejo and JP put it:

“Performance is part of the product. It’s what makes the user stay and buy.”

And:

“Google updates its metrics all the time. You have to stay alert.”

Performance is not a one-time job—it’s a continuous practice.

Closing: The Future Is Faster—and Pyxis Wants to Drive It

The talk made one thing clear:
Web speed is not a trend.

It will keep growing because:

• standards get tougher

• technologies allow deeper optimization

• Google continually evolves metrics

• users expect instant results

Pyxis positions itself as a space that:

• blends engineering and business strategy

• monitors the market

• experiments with new tools

• embeds performance from day zero

• helps clients build fast, competitive digital platforms

Web performance is not just about speed:

It’s about vision, strategy, and design.

And Pyxis is committed to giving every client—big or small—the speed their business needs.