Senior Product Designer currently working at Oplit

Guillaume Caillet — 7+ years of experience — Based in France

Who am I?

My journey into design started way before any formal training — back when I was a kid playing Counter-Strike on the family computer, I wasn't just into the game; I was fascinated by the branding around pro teams like SK, NiP, Fnatic, and VeryGames. I started creating logos and nicknames for my teammates using Photoshop 7 (yes, I was only 6). That's where the story began.

Over time, I grew more curious about how visual systems work and how beautiful things are built. After a (brief and not-so-passionate) detour through an accounting degree, I realigned myself with what had been driving me for years and pursued studies in Design and Engineering.

Today, I'm a Senior Product Designer with 7+ years of experience across industrial, agency, and SaaS environments — from Airbus to PrestaShop, via BeApp and La Capsule.

I specialize in Design Systems, Design Ops, and setting up user research operations that empower teams to make better decisions. My approach combines craft, structure, and collaboration — always with a focus on scaling design sustainably.

My goal is simple: to help teams build consistent, scalable, user-centered products — and to make design a core driver of product performance and team alignment.

Professional Experiences

Sept. 2025 — Now
Senior Product Designer Oplit
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Oplit is an Industry 4.0 scale-up helping transform industrial planning and scheduling through product design.

Structuring and evolving the Design System to ensure consistency, scalability, and cross-team adoption. Designing experiences that make industrial complexity simple, intuitive, and efficient. Strengthening collaboration between Design, Product, Tech, and Operations to accelerate decision-making and innovation.

Impact: Improved product scalability, better leverage of user insights, and direct contribution to Oplit's growth in the Industry 4.0 market.

June 2022 — Aug. 2025
Product Designer PrestaShop
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Sr Product Designer & Design System Lead (2024)

Progressively structures and deploys the research system across PrestaShop. Responsible for structuring and making the tools, templates, and user data operationally available so product teams can access them quickly and efficiently. The aim is to provide efficient access to user search when designing PrestaShop products for our 300k+ merchants.

Also working on structuring the Design System to make it robust, flexible and scalable. Proposing areas for development, structuring the team around the project and giving visibility to what we're doing.

Design System contributor (2023)

Involved in structuring and implementing the PrestaShop Design System. Working on the monitoring, implementation, and use of components and design tokens by everyone who uses the design system, as well as the components designed by the Product Designers.

Product Designer (2022)

Within the Customer Platform team, working on the design and improvement of the user experience through the user account and, more generally, the login experience.

June 2021 — June 2022
UX/UI Designer BeApp
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In charge of UX at Beapp, working mainly with the UI designer and in contact with all the people involved in the various customer projects (PO, Business, Tech).

Designing experiences for different types of clients in the healthcare, automotive, food, institutional, and other sectors. Running creativity, immersion, and co-creation workshops. In charge of user research and testing.

Oct. 2020 — June 2021
UX Designer Consultant La Capsule
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Work as a UX consultant for companies looking to improve their user experience.

Sept. 2018 — June 2020
UX Designer Airbus Atlantique
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Joined the team of UX/UI designers (UXiD) as part of a process to digitalize the Airbus Group. The team designs and redesigns processes as well as business applications and HMIs, putting people back at the heart of their design.

Responsible for disseminating UX guidelines and best practices throughout the group. Collecting user requirements, participating in the design of business applications, organising information architecture, and working in collaboration with IT and other departments.

March 2018 — Aug. 2018
UX Designer — Stage SNCF
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Working as a UX designer in section 574 (innovation) at the SNCF in Nantes. In charge of designing personas, user paths, and screen ergonomics for different applications.

Aug. 2015 — Sept. 2017
UX Designer — Work-study StéreoSuper
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An apprentice for 2 years and trained as a web designer with a specialization in UX design, working on several projects and building up solid experience in a field I'm passionate about.

Other experiences

2025 — Now
Teacher Ecole de design Nantes Atlantique
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Teaching the basics of UI Design to young designers.

2024 — Now
Mentor ADPList
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Helping designers, no matter their seniority, to grow and giving them feedbacks about their projects or career perspectives.

2021 — Now
Speaker ECV Nantes (Master 2 UX Design)
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  • Eco-design & Design System 2023, 2024, 2025 (Speaker)
  • Design System '22-'23 (Annual project) — 100% students graduated
  • User Research Methods '21-'22 (Lecturer)
2020 — Now
Freelancing
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Studies

2017 — 2020
ECV Nantes
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Master 2 — UX Design
Bachelor — Design (L3)

2015 — 2017
CESI Nantes
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Web-Concepteur

Articles

I have written a few articles on various subjects, such as design, design systems, and user research.

Guillaume CAILLET on Medium →

Curriculum Vitae

Download CV (PDF) →

Projects

← Back to projects
Case Study PrestaShop

PrestaShop Design System

Structuring and development of the PrestaShop Design System. Provide product and core teams with access to a system that enables them to design coherent, fluid and easily structured experiences.

Design System Product Design Research UI Design UX Design
100% of product squads use the DS in design
80% adoption in tech teams
-50% reduction in development time
PrestaShop Design System — Project cover

Situation

When I joined in June 2022, the PrestaShop "design system" was a set of advanced UI kits in Figma, not shared as a true library. Product designers worked with their own components, tech teams used a separate framework, and interface consistency was weak.

With multiple touchpoints (main product, help center, marketplace, academy), alignment was critical to scaling both product and brand.

Tasks & Actions

  • Structured the design system team and implemented shared ownership around a unified workflow.
  • Set up contribution processes, component review cycles, and regular design-tech alignment meetings.
  • Built a transparent Kanban in Notion, accessible to both design and tech, to track every component request and status.
  • Audited the existing system and produced actionable recommendations to realign the system for future growth.
  • Pushed adoption of documentation standards, making documentation a Go/No-Go criterion for any new component.
  • Introduced and started implementing design tokens, following best practices for primitive and semantic layers.

Results

  • Implementation of design/tech contribution processes, documentation, comprehensive auditing, governance, and shared Kanban.
  • Initial implementation of design tokens on test projects (inspired by Nathan Curtis).
  • Reduction in design/documentation debt, alignment with tech on nomenclature.

Next Steps

  • Ongoing documentation standardization across all components.
  • Rollout of experience libraries for specialized squads, maintaining brand and UX alignment.
  • Continued monitoring of DS adoption and iteration of governance processes.
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Case Study PrestaShop

PrestaShop Customer Account

Unification and redesign of the PrestaShop user account, previously split into three separate accounts (Back Office, Marketplace, Business Care).

Product Design Prototypage Research UI Design
3 → 1 accounts unified into a single customer account
0 support requests needed for basic account updates
PrestaShop Customer Account — Project cover

Situation

PrestaShop users struggled to manage their interactions due to three separate accounts: Back Office for shop management, Marketplace account for module purchases, and User account for business care subscription invoices.

These fragmented systems created confusion, inconsistency, and inefficiency. Basic actions like updating emails or passwords required users to contact technical support, leading to unnecessary delays.

Back Office — Employee profile page
Back Office — Employee profile (before)
Marketplace Addons — Account page
Marketplace Addons — Account (before)

Tasks & Actions

  • Led exploratory user research, competitive benchmarking, and co-creation workshops to pinpoint pain points and user needs.
  • Oversaw the consolidation of disparate user databases into a single source of truth.
  • Redesigned the UI to clearly distinguish personal and business information.
  • Prioritized must-have features: self-service for updates, account deletion, and unified billing management.
  • Streamlined onboarding by encouraging Google account creation to reduce friction.
Unified account — Personal information
Unified account — Personal information
Unified account — Business information
Unified account — Business information
Unified Account — Final design
Unified Customer Account — Final design

Results

  • Full user autonomy over data, eliminating dependency on support for updates.
  • Data consistently synchronized across all PrestaShop services.
  • Increased user satisfaction through positive feedback.
  • Streamlined processes for billing and account management.
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Case Study PrestaShop

Sign in / Sign up Flow

Redesign of the account creation and connection flow to make it fluid and simple throughout the PrestaShop product.

Product Design Prototypage Research UI Design
-50% authentication errors (7k avg vs 15k before)
-50% flow length reduction
50% of logins via Google SSO within 6 months
PrestaShop Sign in/Sign up Flow — Project cover

Situation

PrestaShop users faced multiple points of authentication (product, marketplace, help center, back office), with no consistent flows or shared data. The lack of synchronization between databases resulted in duplicate accounts and authentication failures.

Until recently, there were 2 connection modes (SSO & Connection by ID). The objective was twofold: increase SSO registrations & connections, and make users understand they only need one PrestaShop account.

Tasks & Actions

  • Conducted an in-depth audit of existing workflows, identifying sources of confusion and friction.
  • Mapped and consolidated all user data sources to a single database.
  • Completely redesigned authentication screens and flows to educate users on the "single account for all PrestaShop" model.
  • Prioritized SSO integration and shortened onboarding to three key steps.
  • Introduced clear error messaging and education around the new account structure.
Sign in — New login page
New sign in page with Google SSO
Sign up — New account creation page
New account creation page
Sign in/Sign up — Full flow overview
Full sign up flow — from account creation to account settings
Sign in/Sign up — Research and user flows
Research — User flows and integration mapping

Results

  • One unified interface across the product for account creation and connection.
  • Support requests related to authentication dropped significantly.
  • Users responded positively to the new, simplified experience.
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Case Study PrestaShop

Store Association Flow

Redesign of the association flow between the user account and the shop, making it transparent and error-resistant.

Product Design Prototypage Research UI Design
600+ successful associations per day
marked decrease in abandonment due to errors
PrestaShop Store Association Flow — Project cover

Situation

The shop association process, particularly for open-source installations, was a major source of confusion. Merchants didn't understand why association was required and abandoned the process — especially when errors occurred.

The association exists because most users have Open Source shops installed locally on their hosting, not always identified as belonging to the owner account. Association creates this connection.

Tasks & Actions

  • Conducted research to identify key pain points and abandonment triggers.
  • Redesigned the flow to require only the necessary information, providing clear guidance and error correction.
  • Modeled the new process on the SaaS "Edition" experience, offering seamless association for recognized shop owners.
  • Prototyped the new flow (including a demonstrative video) and validated improvements with stakeholders.
Store Association — Research and flow mapping
Research — Flow mapping and wireframes
Store Association — Current production flow
Current production flow — Association success path
Store Association — New workflow
New association workflow — Simplified steps

Results

  • Major improvement in user comprehension and reduced frustration.
  • Most shop traffic now flows through the updated payment platform and onboarding.
  • Unified the experience with the "Edition" SaaS model for consistency.