Web application & theme platform

Smily Website Platform

Smily needed a way to manage and evolve hundreds of customer websites without maintaining each one as a separate implementation.

Okzea helped turn that model into a shared, versioned website platform: one core system, reusable custom designs, structured per-site customization, safer upgrades, and tooling built to support continuous releases.

The result is a platform serving more than 300 active websites, with more than 190 theme releases shipped since 2019.

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Overview

Smily, formerly BookingSync, gives vacation rental managers a hosted direct-booking website connected to their property management software.

Okzea worked as an embedded technical partner within Smily’s Experience team from 2017 to 2026. The engagement initially focused on theme architecture, custom designs and the website editing experience, before progressively expanding across the wider website platform, including product features, maintenance, internal tooling and technical decisions.

Over time, Okzea took on an increasingly central role in the technical ownership and evolution of the website platform.

Project details

The challenge

Every website ran its own editable copy of the theme, making platform-wide improvements difficult to deploy safely.
Updates and fixes had to be reapplied manually per website, often taking days and risking existing customizations.
A simple request such as adding a tag manager snippet could involve three people and require a new theme release.
Fonts, colors and layouts were hardcoded, so every custom design started as a one-off implementation.

A shared platform without losing customization

Smily needed a way to improve every customer website from a shared codebase without overwriting each site’s design, configuration or integrations.

The solution was a layered theme architecture where the shared theme remained the source of truth and website-specific changes lived outside the theme code.

The core theme provides the layouts, components, snippets, scripts, styles and translations shared across websites. Variants can change, omit or override parts of that core, while structured options and plugins provide the final layer of customization for each website.
Every editable option is described in JSON Schema. The builder generates its editing interface from that schema and validates every change against it.
25 plugin hook points per theme let the support team inject tracking tags, styles or markup at precise locations without modifying templates.
Each release is built once by CI, versioned and published as a package. Every website receives a deployed instance of that release while its own options and plugins remain separate.
During an upgrade, the platform applies the new release and merges the website-specific configuration onto the updated structure. Existing sections, layouts and values are preserved while newly required fields are added safely.

Custom designs without duplicated code

Since theme v3 in 2022, custom designs have been built as child themes layered on top of one shared core.

A child theme contains only the files it changes, such as a stylesheet, component or template. Everything else is inherited from the core.
This means a custom design no longer requires a complete copy of the theme. Shared fixes and improvements remain in the core and reach every child theme with the next release.
Around 27 custom designs have been produced with this model so far.

Nine years of platform evolution

2017
Joined the Experience team and took over the first-generation theme, shipping the first custom designs for customers alongside homepage, calendar and search improvements.
2018
Cleaned up the theme foundations, replacing the legacy Sass mixin library with Bootstrap components, while custom designs kept coming.
2019
Theme v2: rebuilt the flagship theme on Bootstrap 4 and turned it into a family of four themes shipped as versioned packages.
2022
Theme v3: a jQuery-free rewrite with web components, JSON search, interactive maps, wishlist sharing, campaign pages and cancellation policies.
2023
Expanded the platform with section management, custom attributes, a media gallery, plugins, best offers and strike prices, GA4 with consent mode, a rentals map and reviews from every source.
2026
Theme v4: a Tailwind-based design system with schema-driven components, presets and editor hooks that map the rendered page back to the option that produced it.

A live, schema-driven website builder

The latest phase of the platform is a new editor for theme v4 websites, bringing theme-related work into one interface alongside a live preview.

Pages, sections, navigation, blog content, translations, media and plugins can all be managed from the same editing experience.
A React editor uses schema-driven fields and a section drawer, with changes reflected in the preview through a message bridge instead of page reloads.
Pages are composed from components and presets, allowing regular users to add sections quickly while keeping structured control available when needed.
Navigation, translations and blog editing are integrated directly into the editor, so content can be edited where it appears.
The AI assistant understands the theme structure. It can explain options, make targeted edits, design a section, generate a complete landing page, write copy or translate content.
A design validator checks every AI proposal against the theme’s actual class manifest and palette, so generated pages only use styles that exist in the theme.

Theme v4 website builder with its live preview

Tooling for a lean product team

Supporting hundreds of websites required tooling that reduced repetitive work and made development and releases easier to manage.

An Electron desktop toolkit builds themes, syncs them to any website through the platform API, manages environments and compares files.
A multi-theme build pipeline, automated unit and end-to-end tests, and a mock server allow themes to be rendered locally without running the full platform.
Automated releases generate changelogs and Slack notifications, while theme-scoped CI deployments prevent one theme release from overwriting another.
The section-management system for the v3 editor was built entirely around JSON Schema without requiring backend changes.
The internal operations console was rebuilt as a React SPA over a JSON API, providing theme installation progress, job status, an audit trail and per-site traffic.

SEO and performance at platform scale

SEO, performance and analytics work was handled at platform level so improvements could be applied across the website product rather than treated as isolated changes.

A sitemap and hreflang rebuild removed more than 900 dead or duplicate URLs on a single website, alongside unique canonical URLs on 404 pages and robots rules for faceted search.
Structured data was added for rentals, reviews and custom pages, together with social sharing previews and localized headings.
A Liquid rendering profiler and drop memoization identified and removed a hotspot costing tens of milliseconds per call on pages that could take seconds under load.
The platform also introduced skeleton screens, asset versioning, AVIF delivery through the image CDN and lazy media payloads.
Analytics and tracking included GA4 with consent mode, Meta Pixel purchase tracking and bot detection for the cookie widget.

Impact

Long-term product partnership: 9 years
Active customer websites: 300+
Theme releases since 2019: 190+
Theme generations: 4
Custom designs built on the shared core: 27
Supported languages: 13

30 shared components
43 snippets
17 page templates
More than 1,000 translation keys per theme
25 plugin hook points per theme

Beyond the platform itself, the work included daily support for the customer success team and hands-on migrations of customer websites between theme generations.

Gallery

Testimonials

“You can hand him a problem and stop carrying it.”
Okzea owned our website platform at Smily for nine years, embedded inside our Experience team.
Building one good website is not hard. Building one on top of a property management system and channel manager, where availability, rates and bookings have to stay synchronized and accurate, gets complex fast. Building one codebase that improves 300 of them at once, without breaking any of them, is the hard part. That is what Okzea built.
190+ theme versions shipped since 2017. 27 custom designs running on one shared core with no duplicated code. 13 languages. Every one of those versions was built once and rolled out across hundreds of paying customers' sites, and our support team did not spend the following week cleaning up after it.
He grew into that. He started on themes and design work, then took on the architecture, the tooling, the release pipeline, the SEO and performance work, and the customer migrations. Our team was small for most of those nine years. His judgment is a large part of why that was possible.
The day he showed me the v4 prototype I was floored. You chat with an AI and it drives the entire builder: the settings, adding and removing widgets, writing the copy, translating it. I had seen Lovable and the other AI site generators, and my problem with all of them was the mess. They ignore your guidelines and hand you the cleanup. Okzea built the thing in between. A strict theme with real rules, and an AI that understands those rules and still makes something original inside them. At scale. Taking that from idea to production ready is stellar.
What I would tell anyone thinking of working with him: you can hand him a problem and stop carrying it. He says what he will do, does it, and flags what is going wrong before you have to ask.
As a CEO & Founder, having someone like that on your team is a gift. If you want something built that still works in five years, work with Okzea.
“Things that used to take weeks took him hours.”
Sebastien is a Swiss Army Knife when it comes to designing and building websites.
With so many years of working with Smily, he has managed to design hundreds of beautiful websites for our property managers.
He is not only a capable engineer, but also works very well directly with customers and crafts solutions to their pain points. Sebastien is also one of the greatest examples I've witnessed when it comes to leveraging AI: things that used to take weeks took him hours. And it was on the tech stack where Sebastien didn't have much prior experience and the end solution as if it was built by someone with years of experience in that technology. That level of quality can be only achieved by excellent engineers and Sebastien is definitely one of them.

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