Case study · client application

BuyStep, a marketplace that ranks its suppliers on reliability.

Professional buyers and manufacturers of energy equipment, in six languages. Every supplier goes through a structured audit, from which the platform derives a score. We wrote the whole thing: portal, user areas, audit engine, subscriptions, administration.

01/BackgroundWhere we started

Finding a supplier is easy; deciding which one is not

The observation comes from the client and fits in one sentence: the real challenge is not finding suppliers, it is making the right decision. For each problem, what the platform does.

01Manufacturers' data is self-declared, and their certifications are hard to compare.A single audit, structured in sections, backed by documents and certificates; declarations are cross-checked against the supplier's history and, if needed, a site visit.
02Comparing prices says nothing about a supplier's reliability.A score calculated from the audit, on three pillars, with explicit scoring rules and risk signals.
03Buyers and manufacturers do not speak the same language.A single portal in six languages, right-to-left script included, with translations held in the database rather than in duplicated files.
04A marketplace lives on subscriptions, and a subscription has a life cycle.Three tiers, collected through Stripe, with every state tracked: active, expired, cancelled, unpaid.

02/What we builtDelivered so far

A portal, two user areas, an audit engine and an administration

A single API serves the public portal and the administration. Every component is delivered with its tests.

01
Public portal. Product catalogue, supplier profiles, categories, search, editorial pages, in six languages.
02
Supplier audit. A single questionnaire in sections, a status for each section, documents and certifications uploaded.
03
Score. Reliability indicators calculated from the audit, with risk signals, including those linked to the European directive on corporate sustainability due diligence.
04
Supplier area. Dashboard, products, audit section by section.
05
Buyer area. Comparison, favourites, messaging, suppliers verified by BuyStep.
06
Subscriptions. Three tiers, full life cycle, SEPA direct debit and bank transfer that can be switched on in the configuration.
07
Administration. Moderation of companies, categories, coupons, subscriptions, actions to handle, audit log, tracking of recurring revenue.
08
Files and search. Object storage with image compression on upload; search through Elasticsearch.

03/Three screensThe live site, and its earlier versions

Three screens, actual size

Screenshots of the portal as it is online, and of earlier versions rebuilt from the code history. Nothing is blurred: the client is named with its consent and these pages are public.

BuyStep home page: headline, supplier search, explore button and audit figures — Screen 01The portal's home page, as it is online. Nothing is blurred.

A portal that states its rule: decide on data

The first screen says what BuyStep is: not a price comparison, a decision system. Behind it come the catalogue, the supplier profiles and the search, in six languages.

Intermediate version of the BuyStep home page: Step Free headline, zero commission, product grid without images — Screen 02An intermediate version of the home page, rebuilt from the code history and restarted in a container. Nothing is blurred. On a phone, the top of the home page.

The same business, a changing technical foundation

Between the first version and the current portal, the database, the framework and the interface were replaced one by one, without rewriting the business domain. The legacy code was removed once the portal had caught up.

Sheet of dated screenshots of the BuyStep home page, from the first version to the current portal — Screen 03Two years of home pages, in order. Each screenshot comes from a real version, rebuilt and restarted; no mock-ups.

Every version was restarted, not redrawn

For this sheet, we extracted versions from the history, rebuilt each one in a container with the tools of its time and captured its home page. The method is described in detail on the blog.

04/TechnologiesWhat we chose, and why

A single API, sealed layers, tests that guard them

The foundation changed twice without rewriting the business logic: that is what the architecture was meant to allow, and what we aim for in all custom software.

InterfaceNext.js for the portal and the administration; server routes hold the session, and the browser never sees the API.
Server.NET 10 API in four layers, whose separation is checked by tests on every build.
DatabasePostgreSQL, translations in the database, versioned migrations; Elasticsearch for search.

TestsUnit tests, integration tests on a real throwaway database, and architecture tests.
DeliveryDocker images for the API, the administration and the portal; deployment by branch, two environments.
OperationsRotating logs, cookie-free audience measurement on our own instance, a maintenance page for interventions.

05/Further readingThe site, and the blog

The platform online, and the details article by article

www.buystep.comThe platform, online Choosing an energy supplier on evidenceWhat the platform does, and where AI really comes in Replaying two years of versions in DockerThe tooling behind the screenshots on this page

What next

A platform with user areas, subscriptions and an administration?

BuyStep was written component by component, each one delivered with its tests. Tell us about your project, and we will tell you what is feasible, with a timeline and a rough price.

Discuss your project

Reply within 24 working hours, from one of the two founders. Or by phone: +33 7 59 96 14 99.