Shopify agency in Paris: why custom-built code beats an off-the-shelf theme

A Shopify store built on a theme bought from the marketplace, whichever one it is, arrives with CSS you will never use and JavaScript sections designed for thousands of different stores, not yours. The agency then fills the theme's gaps with apps: one for reviews, one for upsells, one for collection filters, one for bundles. Each app injects its own scripts when the page loads, and none of them knows what the others are doing.

The result shows up in the site's real-world speed: an LCP that often exceeds 4 seconds on mobile, a CLS that makes buttons jump under a shopper's thumb. This is not an argument against Shopify themes, some are well built, but a structural point: a generic theme plus stacked apps produce a store whose speed depends on third-party vendors you do not control, not today and not in a year.

The Paris market has several distinct profiles, and mixing them up means comparing quotes that have nothing to do with each other. Large certified agencies mostly work with mid-sized to large brands, with solid processes and production handled in-house, but rates and timelines built for five- or six-figure projects. Generalist agencies offer Shopify builds as one service among many, with a purchased theme and a stack of apps as the technical foundation.

Independent studios, which is where Sonho sits, bet on a single point of contact from the first meeting to launch, hand-written code, no unnecessary paid apps, and delivery in six weeks on average. Knowing where your project stands helps set a realistic budget: the full breakdown is in our guide on Shopify build pricing.

Here is an honest comparison between the two approaches, in orders of magnitude drawn from market practice and Sonho's pricing for a mid-sized store. The theme looks cheaper at first, with development limited to basic customization. That is exactly where its advantage stops.

Over three years, stacked apps often erase the initial cost gap, sometimes they exceed it. These figures are not a guarantee, every store is different, but the logic stays mechanical: fewer third-party scripts loading means fewer HTTP requests, which means a faster site. To dig into the exact causes of a slow store, this guide covers the most common reasons.

A standard Shopify theme comes with a visual editor and drag-and-drop sections. That feels reassuring at delivery. But as soon as you step outside the frame the theme allows, you need a developer again, and when the theme gets a major update, whatever customization was built on top of it can break overnight.

A custom-built store, with no no-code tool, works the other way around: the code is readable, documented, and the client's team is trained to manage content from Shopify's native interface (products, collections, pages, metadata) without depending on Sonho for every routine editorial change. That is real autonomy, not the surface-level autonomy of a visual builder that hides complexity until the day it resurfaces. The actual workflow of a six-week build is described in this guide.

Google has used LCP, CLS, and INP as ranking signals since 2021. That is not a technical footnote for a brand investing in search or in paid ads: a slow site drags down both organic rankings and the quality score of paid campaigns, which translates into a higher cost per click. A second front is opening at the same time: AI assistants, which are starting to answer purchase questions by citing brands and stores.

A store with no Schema.org markup, or with product pages too thin on detail, stays invisible to these systems. That is why SEO, AEO, and GEO are not a layer added afterward at Sonho: they are built directly into the code while the store is built. The details are on /services/seo-aeo-geo, and the specific case of Shopify is covered in this guide.

Most Shopify projects start with an estimated quote. Extras pile up as the build goes: one more bundle page, a filter to rework, and the final invoice often ends up several tens of percent above the initial budget. We made a different choice: a fixed quote scoped before the work starts, covering the defined perimeter and not moving from there.

This is not a promise of perfection, it is a discipline of scoping upfront that forces the right questions before the first line of code gets written. The trade-off: if a project is vague at the start, we spend time clarifying it together before naming a figure. Other criteria for reading a quote before you sign are covered in this guide.

Sonho is an independent studio based in Paris. One team designs and codes custom-built Shopify stores and Next.js showcase websites for French brands: design, development, and SEO/AEO/GEO handled together, from brief to launch, in six weeks on average. What we don't do: projects for very large brands that need complex integrations or a dedicated, full-time multidisciplinary team.

For that, a larger certified agency is better equipped, and we say so before signing rather than midway through. What we do well: a clean, fast store, hand-coded, with no unnecessary apps, delivered with a fixed quote set before the work starts and autonomy training included at delivery.

Grillé saw sales triple compared with its previous site, with around €200 of app subscriptions cut along the way. Pimo Care cut its mobile LCP by 1.8 seconds after a bilingual France/Switzerland redesign delivered in six weeks. The right time to reach out is when you know what you want to sell and to whom, but your current store is slow, generic, or stuck paying for an app stack that costs too much every month. The full offer is on /services/e-commerce, and you can write to us through /contact to talk it over.