Custom development: solutions tailored to your business needs
Websites, business software, ERP, AI and UX/UI — designed for your teams. Castelis designs, develops and integrates custom solutions adapted to your IS and processes. From idea to deployment, with expert teams available on a staffing basis.
From MVP to production
Native IS integration
Visible business impact
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From requirements to production
We always start from a concrete need: a process to streamline, an experience to improve, data to leverage. Each project is scoped to deliver quickly what truly matters, then to evolve the solution at the pace of your usage.
In project mode or on a remote staffing basis, our teams integrate into your context and support you from the first mockup to production deployment.
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UX/UI & product design
Interfaces designed from the actual usage patterns of your users, not assumptions. We work upstream of the development teams to map out journeys, prototype and validate before coding — reducing costly rework and securing functional decisions.
- Fewer costly development iterations
- Better user adoption
- Consistent interfaces maintained over time
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Showcase and e-commerce websites
Create or modernize your online presence with sites focused on your objectives — whether generating leads, selling online or deploying a large-scale multi-site architecture. We choose the technology based on your actual needs, not the other way around.
- Fast, secure and easy-to-manage websites
- Editorial independence for your teams
- Optimized performance and conversion
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Software & business applications
We start from your actual use cases to design tools that fit your processes. Each software is modelled around what your teams really do day to day — to eliminate friction, reduce errors and free up time for more strategic tasks.
- A tool aligned with your actual business processes
- Fewer errors and manual data entries
- Productivity gains from day one
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Data & AI solutions
We design AI solutions rooted in your business processes. Rather than starting with a technology, we start with your problem: the right approach may be machine learning, generative AI, vector search or a combination — depending on what truly creates value.
- Better-informed decisions, faster
- Automation of low-value tasks
- Controllable and scalable solutions over time
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ERP audit and integration
An ERP project is a long-term commitment for your organization. Before choosing or integrating a solution, an independent audit avoids unpleasant surprises. We analyze your processes, evaluate market solutions and support you through to production.
- Project secured with an independent perspective
- Informed decisions before committing budgets
- Business processes aligned with the chosen solution
/ Concrete projects, measurable results
Discover how our clients have transformed their data into performance drivers, streamlined their processes and strengthened their digital presence through tailored projects.
SNCF | Optimizing the fine recovery rate
Machine learning applied to fine recovery to optimize targeting and reduce processing costs.
Prodistribution | Consolidating group accounting data
Centralized accounting interface system to automate financial flows for 150 companies under the Picard, Casino and Franprix brands.
Groupe Leclerc | Security and performance of the e-commerce website
Unification of e-commerce and marketplace sales on a geo-redundant cloud platform.
/ An ecosystem to go further, faster
We work with the leading tools and platforms in each domain: front-end frameworks, enterprise CMS, AI platforms and ERP solutions. These expertises accelerate your projects and secure integrations.
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FAQ
A CMS is the right fit when you need editorial independence, rapid deployment or multichannel publishing. Custom development becomes necessary when your functional needs or IS constraints go beyond what a standard tool can natively offer.
We help you identify the right approach during an initial scoping phase, with no technological bias.
An audit is valuable as soon as you lack a clear view of the risks, the gaps between your processes and the target solution, or when the project is already behind schedule. It provides an objective diagnosis before committing significant resources.
We intervene both upstream of a new project and during deployment to bring back on track what is drifting.
Not always — and that is precisely why our approach starts with the problem, not the technology. We assess what makes sense given your data, processes and goals. Sometimes a well-defined business rule is more effective than a complex model.
When AI is relevant, we choose the approach suited to the use case: anomaly detection, semantic search, content generation, decision support, workflow automation.
Ideally from the scoping phase — to structure journeys and secure functional decisions before coding. On an existing platform, UX involvement helps identify friction points and optimize the experience without starting from scratch.
Our designers work in close collaboration with development teams to deliver directly implementable interfaces.
Let's talk about your project
Choose the type of project that best fits your needs to start the conversation
