Callixte is available for hire
Hire CallixteCallixte Girard
Verified Expert in Engineering
Full-stack Developer
Paris, France
Toptal member since May 13, 2025
Bio
Callixte is a senior full-stack developer with over seven years of experience across diverse industries, including energy, legaltech, hiretech, eCommerce, FMCG, and real estate. He excels at building robust, scalable applications while adhering to SOLID principles and clean architecture. Clients particularly value Callixte's commitment to bug-free deliverables, transparent reporting, and pragmatic approach to software development that balances technical excellence with business needs.
Portfolio
Valsoft
Vue, .NET, Umbraco, CMS, MySQL, Windsurf, Tailwind CSS, Coding...
Engie France
Python, React, Next.js, Claude, GitHub Copilot, GitHub Actions...
LegalPlace
React, NestJS, Node.js, TypeScript, PostgreSQL, TypeORM, GitLab, GitLab CI/CD...
Experience
- React - 6 years
- TypeScript - 5 years
- Node.js - 5 years
- Python - 5 years
- PostgreSQL - 5 years
- Next.js - 4 years
- NestJS - 4 years
- Cursor AI - 2 years
Work Experience
Front-end Vue/.NET Developer
2026 - 2026
Valsoft
- Joined a 6-month engagement with Thatcher Technology Group (TTG), a Valsoft company, to stabilize a large direct-sales eCommerce platform serving both end customers and a network of sales consultants.
- Resolved around 150 tickets with the team, many of them complex bugs stacked on top of bugs, and ended a long cycle of regressions where each fix introduced new issues.
- Introduced AI coding guidelines and project rules for Windsurf, where none existed, so the AI assistant followed the codebase's conventions and produced consistent, reliable code on a fragile legacy platform.
- Worked across a complex multi-repository architecture: a Vue/TypeScript component library consumed by a .NET app, with front-end components in both Vue and .NET, all integrated with the Umbraco CMS.
- Maintained Vue components that non-technical users could reuse and edit directly from Umbraco, including translated pages and sections.
- Improved key consultant-facing features, making it easier for consultants to manage their sales, teams, and customers.
- Improved mobile display, visual consistency, and overall fluidity significantly, refactoring legacy code on the go without risky rewrites.
- Met every deadline on time or early, going the extra mile when needed.
Technologies: Vue, .NET, Umbraco, CMS, MySQL, Windsurf, Tailwind CSS, Coding, Software Development, Front-end, Front-end Development, Back-end Development, Responsive Web Design (RWD), Web Development, Artificial Intelligence (AI), Vite, Agentic AI, Agentic Coding, Generative Artificial Intelligence (GenAI), OpenAI, AI-assisted Development, Code Review, Code Auditing, eCommerce, AI Agents, C#, Design Systems, SQL, HTML5, Visual Studio, Visual Studio Code (VS Code)
Full-stack React/Python Developer
2025 - 2026
Engie France
- Developed features across a React, Next.js, and TypeScript front end and a Python/Flask back end for an internal app that models district heating and cooling networks at city scale, including energy mix modeling.
- Worked daily with AI coding agents (Claude Code, GitHub Copilot) to ship entire parts of the app 2 to 3 times faster, reviewing every change and using AI-generated unit tests as guardrails to keep code quality high.
- Integrated an AI chatbot connected to ENGIE's internal documentation into the app's interface, giving users instant business or technical answers without leaving their workflow.
- Built interactive maps and charts with Mapbox and Recharts, using data decimation to keep them fast on large datasets.
- Took part in rewriting the legacy front end in Next.js and in building a backend for frontend (BFF) that wraps a 10-year-old CubicWeb/RQL legacy core.
- Upgraded a years-behind internal library by 8 versions in just 2 afternoons without blocking the team, removing long-standing bugs and workarounds.
- Wrote unit tests with Pytest and Vitest, and made the Playwright end-to-end tests more robust and efficient.
- Owned my tickets end to end, up to production, and regularly acted as Captain Run, Security, and Delivery on Demand for the team's releases.
- Collaborated in an international, Agile environment with ENGIE teams in Belgium, Italy, and Brazil.
- Used AI agents for thorough code reviews and took part in regular internal workshops on agentic coding practices and new AI tools.
Technologies: Python, React, Next.js, Claude, GitHub Copilot, GitHub Actions, Amazon Web Services (AWS), TypeScript, Flask, Mapbox, Recharts, Pytest, Vitest, Vite, Unit Testing, Playwright, End-to-end Implementation (E2E), Docker, Figma, Agile, Jira, CubicWeb, RQL, Poetry, Coding, Product Management, Software Development, Front-end, Back-end, Full-stack, Front-end Development, Back-end Development, Full-stack Development, Tailwind CSS, Object-oriented Design (OOD), Responsive Web Design (RWD), Web Development, Architecture, Technical Leadership, Artificial Intelligence (AI), Claude Code, Delivery Management, AI Chatbots, Generative Artificial Intelligence (GenAI), APIs, REST APIs, API Integration, Agentic AI, Agentic Coding, Code Review, Code Auditing, AI Agents, Model Context Protocol (MCP), Express.js, Design Systems, API Design, HTML5, Visual Studio App Center, Visual Studio, Visual Studio Code (VS Code)
React/Node.js Developer
2025 - 2025
LegalPlace
- Developed and shipped new features on a NestJS/C# back end and a React front end while ensuring performant, accessible UIs for complex financial workflows.
- Designed and maintained robust RESTful APIs to integrate with external banking partners and internal legal service modules.
- Collaborated daily with product managers, UX designers, and adjacent engineering squads to align on data models, authentication flows, and deployment strategies.
- Followed and contributed to development best practices, including test-driven development (TDD), code reviews, shared documentation, and CI/CD pipelines.
- Used Cursor daily for AI-assisted development and test generation, and shared practices with the team to boost productivity without compromising code quality.
- Drove continuous improvement of development processes through retrospectives, metrics tracking, and knowledge-sharing workshops.
Technologies: React, NestJS, Node.js, TypeScript, PostgreSQL, TypeORM, GitLab, GitLab CI/CD, Agile, Scrum, Storybook, RTK Query, Cursor AI, Unit Testing, Jest, API Integration, TanStack Router, TanStack, User Interface (UI), Databases, Front-end Development, Back-end Development, Full-stack Development, Tailwind CSS, Software Architecture, CSS, APIs, Banking as a Service (BaaS), Amazon Web Services (AWS), HTML, Large Language Models (LLMs), Pixel Perfect, Responsiveness, Artificial Intelligence (AI), PL/pgSQL, Pipelines, Microservices, GraphQL, REST, CSS3, CSS Animations, Figma, CSV, REST APIs, Serverless, Gemini, Google Cloud Platform (GCP), .NET, Go, AI Tools, Non-relational Databases, Relational Databases, Claude, Active Directory (AD), Azure SQL Databases, Jira REST API, Java, BigQuery, Springbot, Laravel, DevOps, C#, Bubble, Low Code, React Hook Form, Single Sign-on (SSO), React Testing Library, Server-side Rendering (SSR), Object-oriented Programming (OOP), Amazon Simple Queue Service (SQS), Datadog, HIPAA Compliance, Payload CMS, RabbitMQ, Radix UI, Sitecore, WCAG 2, Mapbox, Geospatial Data, Automation, Google Workspace APIs, Salesforce API, Code Review, Coding, GraphQL API, Legal Technology (Legaltech), Software Development, Front-end, Back-end, Full-stack, Object-oriented Design (OOD), JSON Web Tokens (JWT), Responsive Web Design (RWD), Web Development, Architecture, Technical Leadership, Vite, Legal, CI/CD Pipelines, AI Engineering, Agentic AI, Agentic Coding, WebSockets, Generative Artificial Intelligence (GenAI), OpenAI, React Redux, React Router, Redux, AI-assisted Development, Startups, AI Agents, Webhooks, Authentication, Authorization, Design Systems, React Native, SQL, HTML5, Visual Studio App Center, Visual Studio, Visual Studio Code (VS Code)
Full-stack React/Node.js Developer
2024 - 2024
Revolt.eco
- Developed new features on the React, Next.js, and NestJS application.
- Achieved rapid and bug-free feature delivery by adhering to industry best practices.
- Used Cursor daily to speed up feature delivery across the Vue, React, and Next.js codebases, carefully reviewing AI-generated code before merging.
- Evolved a PostgreSQL database using Prisma for seamless migrations.
- Reviewed code contributed by other developers during pull requests.
Technologies: React, Next.js, Node.js, TypeScript, PostgreSQL, Git, GitHub, JavaScript, Front-end, Back-end, Full-stack, Databases, RTK Query, Cursor AI, Unit Testing, Jest, TanStack Router, TanStack, User Interface (UI), Front-end Development, Back-end Development, Full-stack Development, Tailwind CSS, CSS, APIs, Dashboards, HTML, Large Language Models (LLMs), Pixel Perfect, Responsiveness, Material UI, Artificial Intelligence (AI), PL/pgSQL, Microservices, Chart.js, REST, D3.js, CSS3, CSS Animations, Figma, CSV, REST APIs, Gemini, CI/CD Pipelines, Architecture, Single Sign-on (SSO), Docker, React Testing Library, Object-oriented Programming (OOP), Amazon Simple Queue Service (SQS), Radix UI, Sitecore, Mapbox, Airtable, Automation, Code Review, Coding, Software Development, Object-oriented Design (OOD), Responsive Web Design (RWD), Web Development, Vite, WebSockets, Generative Artificial Intelligence (GenAI), React Redux, React Router, Redux, AI-assisted Development, Early-stage Startups, Startups, Authentication, Authorization, NestJS, Design Systems, HTML5, Visual Studio, Visual Studio Code (VS Code)
React/Node.js Developer
2021 - 2023
Kador.io
- Developed the front and back end with React, Next.js, NestJS and .NET.
- Participated in and facilitated user exchange sessions following Agile methodology to comprehend their needs and address inquiries.
- Migrated the application's database to PostgreSQL.
- Migrated the existing app from low-code platforms using Retool for the front end and Xano for the back end and database.
- Set up CRON jobs to define regular automated background actions and procedures.
- Utilized Retool occasionally for rapid prototyping and drafting purposes.
- Enhanced, restructured, and improved the existing monolithic and sluggish Retool and Xano application.
- Developed a Chrome extension for LinkedIn, complementary to the main app, in Vanilla JavaScript without external libraries.
Technologies: React, Next.js, Node.js, JavaScript, PostgreSQL, MongoDB, Full-stack, Front-end, Back-end, REST, Retool, Xano, Chrome Extensions, API Integration, TanStack Router, TanStack, User Interface (UI), RTK Query, Databases, Front-end Development, Back-end Development, Full-stack Development, Jest, Tailwind CSS, Software Architecture, CSS, APIs, Dashboards, OpenAI API, HTML, Vue 3, Large Language Models (LLMs), Pixel Perfect, Responsiveness, Material UI, Artificial Intelligence (AI), Supabase, PL/pgSQL, FastAPI, CSS3, CSS Animations, Figma, Figma to React, CSV, REST APIs, Serverless Framework, AI Tools, Non-relational Databases, Relational Databases, .NET, Active Directory (AD), Java, BigQuery, Laravel, Architecture, React Hook Form, Payload CMS, Radix UI, WCAG 2, Vue, C#, .NET 8, Code Review, Coding, Product Management, Software Development, Object-oriented Design (OOD), JSON Web Tokens (JWT), Web Development, XML, Elasticsearch, React Redux, React Router, Redux, Product Roadmaps, Early-stage Startups, Startups, Code Auditing, Webhooks, Authentication, Authorization, NestJS, Design Systems, API Design, HTML5, Visual Studio, Visual Studio Code (VS Code)
React/Python Developer
2021 - 2022
Needl
- Implemented the matchmaking algorithm between buyers and suppliers.
- Set up React applications with the Next.js framework to manage registrations and recommendations for CSMs, facilitating their client management.
- Studied and optimized the process of registration and animation of business meeting virtual events.
- Studied and implemented a key business data visualization app for stakeholders.
- Participated in integrating the matchmaking algorithm and data processing scripts on AWS Data Lab in collaboration with a data engineer.
- Prototyped solutions with Retool to provide a quick way for CSMs to see and modify key business data for their clients.
Technologies: React, Next.js, Python, Django, JavaScript, SQL, MySQL, Full-stack, Front-end, Back-end, Data Analysis, Pandas, NumPy, Retool, Git, Unit Testing, Pytest, API Integration, TanStack Router, TanStack, User Interface (UI), RTK Query, Databases, Front-end Development, Back-end Development, Full-stack Development, Tailwind CSS, Software Architecture, CSS, APIs, Analytics, Dashboards, Amazon Web Services (AWS), HTML, Pixel Perfect, Responsiveness, Material UI, Pipelines, Flask, REST, Snowflake, AWS Lambda, CSS3, Figma, Figma to React, Shadcn, CSV, REST APIs, Data Transformation, Serverless, Gemini, Google Cloud Platform (GCP), Serverless Framework, CI/CD Pipelines, Claude, Azure SQL Databases, Laravel, Low Code, Docker, Server-side Rendering (SSR), Object-oriented Programming (OOP), HIPAA Compliance, Sitecore, Airtable, Google Workspace APIs, Salesforce API, Coding, Product Management, Software Development, Object-oriented Design (OOD), Web Development, Elasticsearch, React Router, Early-stage Startups, Code Review, Startups, Code Auditing, Webhooks, Authorization, NestJS, Express.js, Design Systems, API Design, HTML5, Visual Studio, Visual Studio Code (VS Code)
Python Developer
2021 - 2021
sundayapp
- Developed a web scraper in Python to collect data from several thousand restaurants.
- Sorted all the data found in the interesting website pages containing new prospective restaurants, including pictures.
- Analyzed and matched this data against an existing database of tens of thousands of entries using the Pandas library.
Technologies: Python, Scraping, Web Scraping, Back-end, Data Matching, Pandas, Selenium WebDriver, Data Analysis, Back-end Development, CSV, Data Transformation, Coding, Software Development, Object-oriented Design (OOD), Startups, Visual Studio, Visual Studio Code (VS Code)
Python Developer
2020 - 2021
French Real Estate Agency
- Developed a scraper to collect real estate data from French cities such as MeilleursAgents. MeilleursAgents is a very challenging site to scrape due to the numerous protective measures they have explicitly implemented against scrapers.
- Stored and updated this data in a PostgreSQL database.
- Visualized the scraped data in a Power BI dashboard.
Technologies: Python, Django, PostgreSQL, SQL, Scraping, Database Design, Selenium WebDriver, Microsoft Power BI, Data Analysis, Unit Testing, Pytest, API Integration, User Interface (UI), Databases, Front-end Development, Back-end Development, Full-stack Development, Software Architecture, CSS, APIs, Analytics, Dashboards, HTML, REST, FastAPI, CSS3, CSV, REST APIs, Data Transformation, Coding, Software Development, Object-oriented Design (OOD), Spring Boot, Apache Maven, Web Development, Code Auditing, HTML5, Visual Studio, Visual Studio Code (VS Code)
React Developer
2020 - 2020
ISEP
- Parsed JavaScript code initially with an AST to generate a comprehensive plan outlining its structure.
- Transformed the plan into colored visual blocks using the Blockly library.
- Converted each code section, including loops, conditions, variables, etc., into a block that could be rearranged and nested.
Technologies: React, JavaScript, Abstract Syntax Trees (AST), Full-stack, Front-end, Blockly, User Interface (UI), Front-end Development, CSS, HTML, Coding, Software Development, Spring Boot
VBA Developer
2017 - 2019
Bouygues Telecom
- Calculated statistics to analyze and optimize an order database.
- Developed corrective scripts for Excel database extracts to rectify inconsistencies automatically.
- Imported and merged various Excel extracts from BO databases.
- Presented results in a structured, clear format to be understandable to the entire non-tech team.
Technologies: Excel VBA, Excel 2013, Analytics, Data Visualization, Dashboards, Data Transformation, PHP, Coding, Software Development
Project History
Vadims.AI —The AI That Understands Your Audience to Make Your Content Convert
Vadims.AI is a SaaS I co-founded with a friend in late 2024 and launched in early 2025.
This is a simple AI-based SaaS that allows influencers to write posts that correspond to their style and structure very easily and quickly. Users have nothing to configure; we have tailored prompt pipelines for each output. Users can also provide additional parameters and examples of their style to make the output even more fine-tuned. Everything is made to simplify their life and make it the easiest way possible.
There is a whole range of output formats provided, each with its specific format, codes, etc: high-value post, side note, tweet, Instagram description, LinkedIn post, newsletter, thread, and even more to come. This was made with Next.js, React, PostgreSQL, and deployed on Vercel. I also included a back office for my partner to update the detailed custom prompts and instructions for our models.
I made all the technical design and realization, while my partner made all the marketing and sales parts. We made the product part together, from a common and iterative reflection. I am also in charge of all the technical support, code coverage, security, and migrating the database while not affecting users in production.
This is a simple AI-based SaaS that allows influencers to write posts that correspond to their style and structure very easily and quickly. Users have nothing to configure; we have tailored prompt pipelines for each output. Users can also provide additional parameters and examples of their style to make the output even more fine-tuned. Everything is made to simplify their life and make it the easiest way possible.
There is a whole range of output formats provided, each with its specific format, codes, etc: high-value post, side note, tweet, Instagram description, LinkedIn post, newsletter, thread, and even more to come. This was made with Next.js, React, PostgreSQL, and deployed on Vercel. I also included a back office for my partner to update the detailed custom prompts and instructions for our models.
I made all the technical design and realization, while my partner made all the marketing and sales parts. We made the product part together, from a common and iterative reflection. I am also in charge of all the technical support, code coverage, security, and migrating the database while not affecting users in production.
Job Apply Assistant — Find, Filter, and Apply to Jobs with AI
https://nurse-offers-assistant.nurse-offers-assistant.workers.dev/Web assistant built with React Native for a nurse friend that finds French nursing job offers and drafts a tailored cover letter for each one. Right now, it is a web React Native app, but it will soon be published on the App Store as well. It pulls live listings from the France Travail "Offres d'emploi v2" API, searches around a chosen city, saves favorites, and generates cover letters from the user's own CV and example letters, keeping every regenerated version in a history. V1 runs as a Cloudflare Worker serving static assets, with storage behind a ports/adapters layer for persistence. It will soon be hosted on Azure and store data in a PostgreSQL database.
Education
2014 - 2019
Master of Engineering Degree in Software Development
ISEP - Paris, France
Skills
Libraries/APIs
React, Node.js, OpenAI API, Vue, REST APIs, Jira REST API, React Hook Form, React Testing Library, Google Workspace APIs, Salesforce API, React Redux, React Router, Pandas, Selenium WebDriver, Vue 3, Chart.js, GraphQL API, NumPy, Blockly, Stripe API, D3.js, Stripe, Recharts, Playwright, React Native for Web, Claude API
Tools
RTK Query, TanStack Router, Figma, Claude, BigQuery, Visual Studio, Git, GitHub, Retool, Prisma, Pytest, Jupyter, Shadcn, Bubble, Amazon Simple Queue Service (SQS), RabbitMQ, Claude Code, GitLab, GitLab CI/CD, Microsoft Power BI, Excel 2013, GitHub Copilot, Vitest, Jira, Windsurf, Apache Maven, Visual Studio App Center
Languages
TypeScript, JavaScript, Python, SQL, HTML, PL/pgSQL, CSS3, Go, Java, PHP, C#, HTML5, CSS, GraphQL, Excel VBA, Snowflake, C#.NET, XML
Frameworks
Next.js, NestJS, Jest, Tailwind CSS, Serverless Framework, .NET, Laravel, Payload CMS, Express.js, Redux, React Native, Django, Material UI, Flask, Spring Boot, .NET 8, CubicWeb, Angular, JSON Web Tokens (JWT)
Paradigms
Clean Code, Clean Architecture, REST, Unit Testing, DevOps, Object-oriented Programming (OOP), Automation, Object-oriented Design (OOD), Responsive Web Design (RWD), Agile, Database Design, Scrum, Microservices, HIPAA Compliance, Model Context Protocol (MCP)
Platforms
Docker, Visual Studio Code (VS Code), Xano, Vercel, Amazon Web Services (AWS), AWS Lambda, Mapbox, Google Cloud Platform (GCP), Umbraco, Webflow
Storage
PostgreSQL, Databases, Relational Databases, Azure SQL Databases, Datadog, MongoDB, MySQL, Elasticsearch
Other
Cursor AI, Software Development, SOLID Principles, Front-end, Back-end, Full-stack, Scraping, Web Scraping, GitHub Actions, API Integration, TanStack, User Interface (UI), Front-end Development, Back-end Development, Full-stack Development, Software Architecture, APIs, Large Language Models (LLMs), Responsiveness, Artificial Intelligence (AI), CSV, Gemini, AI Tools, Non-relational Databases, Active Directory (AD), Springbot, Architecture, Single Sign-on (SSO), Server-side Rendering (SSR), Sitecore, WCAG 2, Airtable, Code Review, Coding, Web Development, Generative Artificial Intelligence (GenAI), Agentic Coding, OpenAI, AI-assisted Development, Early-stage Startups, Design Systems, Hexagonal Architecture, Data Analysis, Analytics, Data Visualization, Dashboards, Banking as a Service (BaaS), Pixel Perfect, Pipelines, FastAPI, Figma to React, Data Transformation, Serverless, CI/CD Pipelines, Low Code, Radix UI, Geospatial Data, Vite, Technical Leadership, AI Engineering, Agentic AI, WebSockets, LLM Integration, Startups, Code Auditing, AI Agents, Webhooks, Authentication, Authorization, API Design, TypeORM, Storybook, Chrome Extensions, Data Matching, Abstract Syntax Trees (AST), Supabase, Vectors, CSS Animations, End-to-end Implementation (E2E), RQL, Poetry, CMS, Legal Technology (Legaltech), Product Management, Legal, Delivery Management, AI Chatbots, Product Roadmaps, eCommerce
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