Guillaume CRESPEL

Guillaume CRESPEL

Javascript developer - Fullstack

38 years old · 16 years of experience

Online résumé : unirakun.fr/en/Guillaume-CRESPEL/

Always on the lookout for new challenges, Guillaume spares no effort in sharing his new knowledge! A modern-day antibody, he challenges his colleagues to bring out the best in them. Beware, this passion is contagious!

Skills

languages

  • Javascript
  • Typescript

frontend

  • ReactJS
  • Apollo
  • CycleJS
  • Redux
  • RTKQuery

backend

  • NodeJS
  • GraphQL
  • Koa / Express
  • Socket.io

tools

  • ViteJS
  • CodeceptJS
  • Cypress
  • Jest

databases

  • MongoDB
  • PostgreSQL

architecture

  • Docker
  • GNU/Linux
  • Kubernetes
  • Azure
  • AWS
  • GCP

Experiences

  1. Full-Stack EngineerAcolad
  2. Founder and CEOKojimo
  3. Interim CTOCockpit Agriculture
  4. Senior Frontend DeveloperDecathlon
  5. Lead Full-Stack DeveloperSGMarket
  6. Lead Frontend DeveloperDARVA
  7. Lead Backend DeveloperDARVA
  8. Lead Frontend DeveloperMetroscope
  9. NodeJS TrainerDARVA
  10. Software Architecture Consultant and DeveloperMetroscope
  11. Frontend Development ExpertSparklane
  12. Lead Frontend DeveloperSanteclair
  13. Lead Full-Stack DeveloperContentFlow
  14. Lead Full-Stack DeveloperSIAO
  15. Lead Full-Stack Developernavalgroup
  16. Developer / Opslaposte

  1. Full-Stack Engineer

    Acolad, on behalf of unirakun

    June 2026 → present · 6 mo

    • Acolad, Europe's leading translation and localization company (now part of the RWS group), helps large companies such as L'Oréal, Air France and IBM deliver their content in more than 500 language pairs, combining AI with the expertise of more than 10,000 linguists.
    • My role: bridging product and engineering, with a deliberately versatile hat within the company.
    • Missions:
      • Full-stack: APIs and services in .NET / C#, interfaces in React and TypeScript
      • AI agents: design and development of an AI agents application, from idea to production
      • Product: scoping needs, UX and prioritization with business teams
      • Cross-team: supporting teams and sharing best practices
    • Key goals:
      • Ship useful features that people actually use, fast
      • Put AI where it brings real value
      • Build reliable, secure and maintainable tools
    • Technologies used:
      • .NET, C#
      • React, TypeScript
      • LLMs, AI agents

  2. Founder and CEO

    Kojimo

    September 2025 → present · 1 yr 3 mo

    • Kojimo, the business accelerator for real estate agents, is a SaaS designed and built by uni rakun. Built for autonomy and control of the process: from valuation to paperwork, all the way to signing the deed, Kojimo simplifies and secures every decision.
    • I own its product vision and engineering: full-time until May 2026, then part-time alongside my missions.
    • What I take care of:
      • Vision and product: user research, scoping, UX, prioritization
      • Technical delivery: architecture, full-stack development, data pipeline, automation
      • Operations and go-to-market: partnerships, compliance, support and feedback loop
    • Key goals:
      • A guided journey from A to Z
      • Actionable data: comparables, local trends, indicators
      • A transparent and reliable experience, built around sellers' real needs

  3. Interim CTO

    Cockpit Agriculture, on behalf of unirakun

    January 2025 → July 2025 · 7 mo

    • Building a SaaS platform for farm business management, which digitises farmers' financial data and helps them improve profitability.
    • Missions:
      • A modern, pragmatic architecture with React, TypeScript and Supabase
      • Automated extraction of financial data with OCR and generative AI
      • A scalable and secure cloud infrastructure
      • An intuitive interface with real-time data visualisations
      • Financial analysis and profitability optimisation
      • Technical leadership of the development team
      • User interviews to validate needs
      • Product roadmap and priorities
      • Contribution to the business plan and strategy
    • Technologies used:
      • React, TypeScript, NodeJS
      • Supabase
      • Generative AI, OCR, prompting

  4. Senior Frontend Developer

    Decathlon, on behalf of unirakun

    April 2024 → June 2025 · 1 yr 3 mo

    • Goal: build a small team to redesign Decathlon's checkout system worldwide.
    • Missions:
      • A modular frontend that adapts to each country's use cases
      • Design and rollout of a hexagonal architecture in a DDD context
      • Communication with peripherals such as RFID bins
      • Integration of the services on existing hardware, in a Kubernetes environment
      • A sound test pyramid, with E2E and integration tests
    • Technologies used:
      • TypeScript, Java
      • ReactJS, zustand, Quarkus
      • PostgreSQL, WebSocket, REST
      • Kubernetes, Datadog

  5. Lead Full-Stack Developer

    SGMarket, on behalf of unirakun

    January 2022 → February 2024 · 2 yrs 2 mo

    • The team I joined at SG Market execution develops a set of applications that serve as a B2B marketplace for financial products
    • Missions:
      • POCs of new applications
      • UX thinking
      • Frontend optimization
      • Feature development
      • Setting up e2e tests
    • Technologies used:
      • Typescript, C#
      • ReactJS, ViteJS, RTK, .Net, Signalr
      • Vitest, RTL, codeceptjs, playwright
      • Azure, K8S, Docker
      • Github, Jira

  6. Lead Frontend Developer

    DARVA, on behalf of unirakun

    January 2020 → January 2022 · 2 yrs 1 mo

    • DARVA is a company specialized in web and EDI (Electronic Data Interchange) solutions, based in Niort and aimed at all insurance professionals.
    • With Nicolas REMISE (DARVA employee) and Fabien JUIF, we helped the BI department make "claims data" easier to access and govern for DARVA's staff as well as for insurance business stakeholders.
    • We are simplifying the visualization and editing of insurers' data structures through a new graphical interface. The goal is to replace an old editing tool and let all staff take back ownership of the knowledge tied to this data.
    • To make this knowledge easier to access, we had to offer a graphical interface that is ergonomic, responsive and easy to understand. We relied on well-known graphical representations such as trees (treeview) and graphs (radial). For editing, where it made sense, we used drag'n'drop. All of it built on the ReactJS ecosystem.
    • Missions:
      • UX / UI workshop
      • Front-End development of the datalake graphical visualization
      • Front-End development of the datalake editor
    • Technologies used:
      • ReactJS, D3 and homemade Layout
      • NodeJS, Typescript, Apollo GraphQL, NestJS, Mongoose
      • Babel, Prettier, ESLint
      • Storybook, Cypress, Jest
      • Docker
      • Github

  7. Lead Backend Developer

    DARVA, on behalf of unirakun

    June 2019 → December 2019 · 7 mo

    • DARVA is a company specialized in web and EDI (Electronic Data Interchange) solutions, based in Niort and aimed at all insurance professionals.
    • As DARVA wants to rely more and more on the mass of data it processes, it needs to integrate that data into a datalake accessible to all departments.
    • To that end, we worked on the storage of claims-related data through a NodeJS batch. It had to be modular, reusable and very fast, since several gigabytes of data must be processed within a short time window.
    • Thanks to NodeJS streams, the data is decoded, deserialized, then saved to a MongoDB database on the fly.
    • To keep the batch's performance under control, we set up metrics to track the velocity of our algorithms throughout development.
    • Once this mission was complete, we built a POC of a graphical interface to better understand the structure of the data involved.
    • Missions:
      • Development of a data integration batch
      • Algorithm and performance metrics
      • Knowledge transfer to the internal teams
      • Proposal of a POC for a graphical interface to navigate the data structure
    • Technologies used:
      • Javascript, NodeJS, MongoDB
      • ReactJS, D3 and homemade Layout
      • Jest and custom performance tests
      • Docker
      • Github

  8. Lead Frontend Developer

    Metroscope, on behalf of unirakun

    July 2018 → March 2019 · 9 mo

    • Metroscope is a startup, a subsidiary of the EDF group, made up of about ten people. Metroscope makes it possible to quickly identify anomalies occurring in the cooling systems of nuclear power plants.
    • With Fabien JUIF, we set up and kept developing the Metroscope product on the Front-End side, remotely. Once it was secured and in production, we trained our successors so that they could be autonomous on the stack we put in place.
    • Missions:
      • Front-End development
      • UX / UI workshop
      • Recruitment support: interviews and choice of successors
      • Training of successors
    • Technologies used:
      • ReactJS / Redux / k-ramel / react-vis / D3.js / JSS
      • Java 8 / SpringBoot
      • Webpack / Babel / ESLint
      • Cypress / Jest
      • Docker / CircleCI / Kubernetes / GKE (google cloud)
      • Github / Jira

  9. NodeJS Trainer

    DARVA, on behalf of unirakun

    November 2018 → November 2018 · 1 mo

    • DARVA is a company specialized in web and EDI (Electronic Data Interchange) solutions, based in Niort and aimed at all insurance professionals.
    • I worked with the BI department to train them in server-side Javascript development with NodeJS.
    • The training took place over 3 weeks. Every Monday, a day mixing theory and practice through various exercises. Every Thursday was dedicated to the participants, so they could freely experiment with what we had done together, with the goal of building from scratch the API of a game we had made ourselves.
    • Simplified training outline:
      • The basics of ES6 Javascript syntax
      • The NodeJS engine and its core modules
      • Explanation of the event loop and asynchronism
      • Using streams
      • Various tools: (Koa2 / mongoDB / socket.io)

  10. Software Architecture Consultant and Developer

    Metroscope, on behalf of unirakun

    March 2018 → June 2018 · 4 mo

    • Metroscope is a startup, a subsidiary of the EDF group, made up of about ten people. Metroscope makes it possible to quickly identify anomalies occurring in the cooling systems of nuclear power plants.
    • With Fabien JUIF, we challenged their MVP in order to produce a first version on a solid and efficient stack, while keeping in mind the needs and constraints of a large organization like EDF.
    • Missions:
      • Thinking through the database structure
      • Thinking through the right Front-end and Back-End technologies to use
      • Setting up the Front-End and Back-End technical foundation
      • Setting up a CI / CD
      • UX / UI workshop
      • Help with project management and agility advice
    • Technologies used:
      • ReactJS / Redux / k-ramel / react-vis / D3.js / JSS
      • Java 8 / SpringBoot
      • Webpack / Babel / ESLint
      • Cypress / Jest
      • Docker / CircleCI / Kubernetes / GKE (google cloud)
      • Github / Jira

  11. Frontend Development Expert

    Sparklane, on behalf of unirakun

    February 2018 → March 2018 · 2 mo

    • Sparklane's development team (based in Nantes) is mostly made up of backend developers (Java/Go). Their frontend stack was getting old. Sparklane asked uni rakun to help them migrate their frontend stack.
    • One of the constraints was to carry out this migration iteratively, so both versions of the application had to coexist. We chose to keep the visual design and to build bridges from AngularJS to React, and vice versa
    • Missions:
      • Development of a technical architecture allowing the migration of an AngularJS front application to a React / k-ramel stack
      • Creation of graphical components to visualize their data (data-viz)
      • Ongoing training of the Sparklane development team on this new stack through codelabs
      • Technical answers to high expectations on this migration from AngularJS (1) to ReactJS
    • Technologies used:
      • ReactJS / k-ramel / react-vis
      • docker
      • nginx
    • Open source contributions:
      • k-ramel - state management for your application, based on Redux and inspired by CycleJS
      • k-intl - quick internationalization of the application
      • hoc-little-router - HoC for configuring the router with Redux

  12. Lead Frontend Developer

    Santeclair

    June 2016 → January 2018 · 1 yr 8 mo

    • Santéclair is a health insurance network with an IT department of 20 people. Santéclair simplifies access to care for its members.
    • As part of their digitalization, I was their Front-End technical lead for the development of web / mobile applications that help people access care.
    • Missions:
      • Development of web and mobile applications
      • Training of the teams in modern Front-End technologies
      • Connecting and partnering with companies offering online booking (Pages Jaunes, MonDocteur, Doctolib)
      • Driver of the company's move to agility
      • Driver of the evolution of processes and of the CI platform
    • Applications built:
      • TrouvTonDoc: Geolocates healthcare professionals outside the santéclair network, calculates the out-of-pocket cost, and allows online appointment booking
      • Devis Dentaire: Allows dental quotes to be made online, aiming at simplified ergonomics and out-of-pocket cost calculation
      • Télémédecine: Connects an insured person with services such as MesDocteurs
    • Technologies used:
      • ReactJS / Redux / redux-saga
      • Java 8 / SpringBoot
      • Webpack / Babel / ESLint
      • Jest
      • CircleCI / Github
      • Docker
    • Open source contributions:
      • k-redux-factory - helps create Redux reducers, actions and selectors
      • kriya - React-Redux component library
      • hoc-little-router - utility to configure redux-little-router
      • roadhog - redux-saga utility for API calls
      • k-redux-saga-tester - utility to test redux-saga sagas

  13. Lead Full-Stack Developer

    ContentFlow, on behalf of Netapsys

    March 2016 → June 2016 · 4 mo

    • ContentFlow is a platform connecting large accounts with advertising agencies.
    • I worked on the product's initialization to produce a coherent MEAN stack.
    • Missions:
      • Setting up the technical architecture on a MEAN stack
      • Front and back development of the application
      • Setting up code quality tools
    • Technologies used:
      • AngularJs (1.5)
      • NodeJs / Express
      • MongoDB / ElasticSearch

  14. Lead Full-Stack Developer

    SIAO, on behalf of Netapsys

    July 2015 → March 2016 · 9 mo

    • The SIAO is the French Integrated Reception and Orientation Service (Service Intégré de l'Accueil et de l'Orientation).
    • I worked on their needs regarding social emergencies, the 115 hotline.
    • Missions:
      • Setting up a modern and coherent technical stack
      • Challenging the ergonomics of the Front-End with the SIAO teams
      • Setting up the CI/CD
      • Training of the Back-End and Front-End development team
    • Technologies used:
      • AngularJs (1.6)
      • Java 7 / SpringBoot / RESTFUL API
      • Maven / Jenkins

  15. Lead Full-Stack Developer

    navalgroup, on behalf of Euriware

    April 2012 → July 2015 · 3 yrs 4 mo

    • Refcoll is a modular application used at DCNS to track the construction of its naval vessels.
    • I worked on the technical foundation for 2 years before moving on to technical-functional needs.
    • Missions:
      • Expertise and customization of Refcoll within Maintenance in Operational Condition and Documentation Management projects
      • Estimates and planning for Refcoll projects
      • Setting up the software forges needed for the development of the various projects
      • Coaching and training of DCNS functional developers and Refcoll application developers
      • Expertise and architecture definition within DCNS for the deployment of Refcoll in their MCO projects
      • Design and development of several customization modules to improve the user experience within the Refcoll application
      • Design and development of a customization module to industrialize and optimize business operations
      • Setting up functional acceptance tests
    • Technologies used:
      • GWT / AngularJS
      • Java 6 / Spring

  16. Developer / Ops

    laposte, on behalf of CGI

    May 2010 → April 2012 · 2 yrs

    • For La Poste's Reinette project, in a 50-person service center, I carried out missions within the maintenance team (TMA) managing La Poste's account and center reference data.
    • Missions:
      • Design and implementation of the architecture of various applications
      • Management of continuous integration platforms, implementation of deployment and deliverable-creation scripts
      • Management of Apache Tomcat and IBM Websphere components
      • Estimating features
      • Coaching a development team
    • Technologies used:
      • Struts
      • Java/J2E, Oracle 10/11g, Sybase, Korn Shell
      • Eclipse, Tomcat 6.0, Websphere
      • Checkstyle, PMD, FindBugs, Junit