What an mvp logiciel sur mesure is, and what it is not
'Mvp logiciel sur mesure' is French for a custom-built minimum viable product: software developed specifically for one problem instead of being assembled from an off-the-shelf package. The appeal is obvious, because you get the workflow you need and nothing else. In the author's view, the main risk is that bespoke work invites scope to grow, which is why careful scope decisions before development starts deserve as much attention as the build itself.
A useful working definition is the smallest product that can be responsibly operated and that produces useful evidence from a real user path. Each part of that phrase limits the project. 'Smallest' constrains scope. 'Responsibly operated' means it runs in a real environment with failure handling. 'Evidence' means it exists to answer a question, not to impress stakeholders.
IVRYN, an independent Paris studio that builds focused products for distinct audiences, publishes the methodology and decision guide this article draws on. The definitions, distinctions and verification practices below come from those public documents; the practical observations added around them are the author's reasoning, not findings from client engagements or any study. Treat the whole as a framework to adapt rather than a proven recipe.
Start with the decision, not the artifact
Before commissioning a custom MVP, write one sentence describing the decision it should inform. If the team still disagrees on how the user flow should work, a prototype is the more suitable tool. If everything depends on whether an API, an algorithm or a hardware integration behaves as hoped, a proof of concept isolates that single risk. An MVP makes sense when the problem, the path and the operating boundary are understood well enough that only real use can teach you more.
This order matters especially for bespoke work. When a developer is already engaged, it is tempting to go straight to 'the real thing'. But building production infrastructure around an untested technical assumption risks paying twice if that assumption fails. Answer these questions before choosing a format:
- Who will use or inspect the artifact?
- Where will it run, and which data may it touch?
- Which result would change the plan?
- What can this result not demonstrate?
Scope the problem boundary before the features
Begin with a specific user, task and context, and write down assumptions, dependencies and exclusions early. For a custom MVP, the exclusions list is often the most useful document in practice. It helps stop 'while we are at it' requests from turning a short build into an open-ended one, and it keeps a polished interface from hiding an undefined problem.
Separate what you have actually observed users doing from what you hope they will do. Then list security, privacy, accessibility and platform constraints early, since they can shape architecture choices such as where data lives or which identity provider you depend on. Collect only the data the feature and its operation require. Every extra field is something you must protect and justify.
Third-party services deserve the same scrutiny as your own code, because each has its own availability, policy and cost constraints. If the MVP includes AI-assisted functions, decide upfront how the interface signals generated output, where a human reviews it, and what happens when the model or provider is unavailable.
Ship small, testable and accessible releases
One suggestion, offered as the author's view rather than a sourced rule, is to plan a custom MVP as a sequence of small releases, each tied to a check you can actually run. The methodology's own principle is that verification is proportional to risk: a release can include automated checks, manual flow tests, responsive visual checks and monitoring of the deployed route. A build that passes locally is not a production release until the public endpoint has been checked.
Accessibility is one of the constraints the methodology asks teams to identify early, and the decision guide notes that an MVP boundary can include accessibility and other safeguards where the context requires them. Critical flows should also receive understandable language, failure states and a recovery path. As a matter of reasoning, if some users cannot complete the path, their behaviour is likely missing from the evidence the MVP collects.
Define measurable outcomes in terms of the user task, for example whether people complete the core path and where they abandon it. Treat laboratory scores such as a Lighthouse result as time-specific measurements, not as guarantees of real-world performance.
The limits: what a custom MVP cannot prove
Three traps are worth naming. A convincing prototype does not prove production quality. A successful technical proof does not prove user demand. A deployed MVP does not prove adoption, revenue or product-market fit. Launching starts evidence collection; it is not the evidence.
In the author's view, custom development adds a limit of its own: ownership. Once the MVP is live, someone must operate it, update dependencies and respond to failures. Planning for that before launch reduces the chance that a successful test leaves you with software nobody maintains. Contract terms, intellectual property and funding questions are outside the scope of this article and call for qualified professional advice.
Worked example and checklist for a custom MVP
Example (hypothetical): a small logistics team wants custom software so drivers can report delivery issues from a phone instead of calling the office. Their decision sentence reads: 'If drivers on one route use the form instead of calling during a four-week trial, we extend it to other routes; if not, we revisit the flow.' The test cannot show whether other teams or companies would adopt it.
Their exclusions for release one are route optimisation, customer notifications and offline sync. Constraints include outdoor phone use, which in this context means large touch targets and readable contrast, and location data is not collected because the form does not need it. The outcome they track is the share of issues reported through the form versus by phone, plus the step where drafts are abandoned.
- One-sentence decision written and agreed
- Prototype or proof of concept completed if flow or feasibility is still uncertain
- Exclusions list signed off
- Data collection limited to what the feature requires
- Failure state and recovery path for each critical flow
- Accessibility constraints identified early and addressed where the context requires
- Outcome metric tied to the user task
- Public endpoint verified, not only the local build
- Named owner for operation after launch
Frequently asked questions
What is the difference between a custom MVP and a prototype?
A prototype explores how a proposed experience should work and can range from a sketch to an interactive flow, but it does not prove production quality. A custom MVP is the smallest product that can be responsibly operated in a real environment to produce useful evidence from a real user path.
Does a successful custom software MVP prove product-market fit?
No. A successful deployment proves that the software was delivered to an environment at a particular point in time. It does not by itself prove adoption, revenue or product-market fit; those conclusions require separate, attributable observations over an appropriate period, interpreted against the decision the MVP was built to inform.
When should a team build a proof of concept before a custom MVP?
Build a proof of concept first when the product depends on one uncertain technical assumption, such as an unfamiliar API, an algorithm or a hardware interaction. Testing that assumption in isolation avoids building production infrastructure around something that may not work, though a technical success still does not prove user demand.
Sources and further reading
These resources provide the wider reference frame. Product statements on this page are limited to the public information provided by IVRYN.



