Roman is available for hire
Hire RomanRoman Cirier
Verified Expert in Engineering
React Developer
Paris, France
Toptal member since August 17, 2022
Bio
Roman is a full-stack engineer with 6+ years shipping web and mobile products end-to-end in TypeScript with React, React Native, and Node.js/NestJS. He owns architecture from database to UI, leading teams on some engagements, building entire platforms solo on others, and increasingly shipping LLM- and vector-search-backed features in production. He's driven by turning ideas into products real users rely on, sweats performance and clean architecture, and holds a dual master's in computer science.
Portfolio
AFG Bank
APIs, API Integration, Full-stack Development, React, Front-end Development...
Bloomflow
React Native, TypeScript, Expo, Zustand, NativeWind, Tailwind CSS, MMKV, Sentry...
Journey - Main
Full-stack, RESTFul APIs, Big Data, NestJS, TypeScript, Google Cloud ML...
Experience
- React - 7 years
- JavaScript - 7 years
- TypeScript - 7 years
- React Native - 6 years
- Node.js - 5 years
- Mobile Apps - 5 years
- NestJS - 3 years
- GraphQL - 2 years
Work Experience
Full-stack Engineer
2026 - 2026
AFG Bank
- Built from scratch, as sole engineer, a WhatsApp chatbot and web app letting AFG Bank customers check balances and transfer money, in a TypeScript monorepo (Next.js, NestJS, PostgreSQL, Redis).
- Designed a channel-agnostic messaging layer on the WhatsApp Business API, so new channels like Telegram plug in without changes to core banking logic.
- Built a zero-retention architecture for banking-grade security: no balances, account data, or OTPs stored or cached, PII scrubbed from all logs, and every sensitive operation recorded in an append-only audit trail.
- Integrated the bank’s core APIs with idempotent retries and failure handling to prevent duplicate transfers, backed by 1,000+ automated tests.
Technologies: APIs, API Integration, Full-stack Development, React, Front-end Development, PostgreSQL, Artificial Intelligence (AI), Payments, Financial Services, Fintech, QR Codes, WhatsApp, Live Chat, French, WhatsApp API, Telegram Messenger API, Voice Recognition, NestJS, TypeScript, Redis, Web Development, Full-stack, Next.js, Back-end, Web Applications, Software Development, Testing, Claude Code, API Development, Agentic Coding, Application Security, Cloud, Back-end APIs, Rest APi, Webhooks
Mobile Developer
2026 - 2026
Bloomflow
- Rebuilt the mobile app from the ground up: migrated from JavaScript to a fully typed TypeScript codebase with a clean architecture, redesigned all core features and animations, and shipped new functionality.
- Designed an AI assistant agent, including conversational chat, voice "add-with-AI" capture, entity disambiguation flows, and recap/reminder.
- Cut cold-load time from 2–3s to near-instant by decoupling rendering from non-critical data fetching.
- Engineered a robust server-state and offline layer with TanStack React Query (persisted to encrypted MMKV storage) and Zustand, plus secure token handling via Keychain/Keystore and biometric local authentication.
Technologies: React Native, TypeScript, Expo, Zustand, NativeWind, Tailwind CSS, MMKV, Sentry, EAS, Artificial Intelligence (AI), AI Agents, CI/CD Pipelines, SaaS, QR Codes, Agentic AI, Claude Code, Agentic Coding, Application Security
Senior Back-end Engineer
2025 - 2026
Journey - Main
- Developed a semantic property search system integrating Vertex AI and Google Places API for intelligent autocomplete suggestions.
- Implemented a viewport-based map endpoint with server-side clustering to optimize mobile performance.
- Built a comprehensive search API with multi-dimensional filtering (dates, pricing, and amenities), orchestrating data across microservices.
- Designed filter metadata endpoints with dynamic facet counts and price histograms for interactive UI.
Technologies: Full-stack, RESTFul APIs, Big Data, NestJS, TypeScript, Google Cloud ML, Vertex AI, AlloyDB, React Native, Google Cloud Platform (GCP), GPS, Data Modeling, Scalable Architecture, REST, Back-end, Claude Code, Software Development, Testing, API Development, Agentic Coding, Application Security, Cloud, Back-end APIs, Rest APi
Full-stack Mobile Developer
2025 - 2025
FleetRover Inc
- Developed the new driver vehicle inspection report (DVIR) feature end-to-end, including API design, CRUD operations, PDF generation, and offline support.
- Implemented the DVIR workflow and UI in both the mobile app (drivers) and the web app (carriers).
- Established error tracking with Datadog in the mobile app.
- Improved the mobile app's reliability and performance, and contributed to PR reviews.
Technologies: React Native, JavaScript, Auth0, Datadog, Amazon Web Services (AWS), Amazon EKS, Amazon Simple Email Service (SES), Amazon RDS, TypeScript, NestJS, PostgreSQL, RabbitMQ, React, Shadcn, Zod, Vite, Expo, EAS, Drizzle, SQLite, NativeWind, Next.js, Tailwind CSS, RESTFul APIs, Analytics, Crash Reporting, Telemetry, CSS, HTML, Data Modeling, Database Structure, Scalable Architecture, REST, Back-end, Claude Code, Web Development, Full-stack, Web Applications, Software Development, Testing, API Development, Agentic Coding, Application Security, Cloud, Back-end APIs, Rest APi
Full-stack Developer
2024 - 2025
Kivid
- Independently designed the architecture and built a NestJS/GraphQL API plus a mobile app, owning data modeling, cloud infrastructure, and deployment pipelines end-to-end.
- Built a single app (with React Native and TypeScript) for both physiotherapists — who prescribe exercise programs, track recovery in real time, and share educational videos — and patients, who follow programs, message their physio, and track progress.
- Migrated data from an old existing data to the new one, reforming data to match the new structure designed.
Technologies: React Native, NestJS, TypeScript, PostgreSQL, Expo, Amazon S3 (AWS S3), Amazon Simple Email Service (SES), Prisma, Front-end, User Experience (UX), UI Design, Scalability, App Store, Google Play Store, Crash Reporting, Amazon Web Services (AWS), React Native Navigation, CI/CD Pipelines, Push Notifications, Data Modeling, Database Structure, Scalable Architecture, Videos, REST, Back-end, Claude Code, Minimum Viable Product (MVP), GitHub Actions, Full-stack, Software Development, API Development, Application Security, Cloud, Multi-tenant SaaS, Back-end APIs
Full-stack Developer
2023 - 2024
Mayoo
- Independently designed and built a three-surface platform: a NestJS microservices API on PostgreSQL, a React web app, and a React Native mobile app, all in TypeScript — owning every layer from architecture to automated deployment with GitHub Actions.
- Built the staff web app for canteen chefs to manage menus, collect student feedback, and track food waste and noise levels, as well as for admins to create content.
- Built the student mobile app to browse and choose menus, access educational content on nutrition and food waste, and send feedback to the chefs.
Technologies: Node.js, NestJS, PostgreSQL, Microservices, React, React Native, TypeScript, Deployment, DigitalOcean, Expo, Prisma, CSS, HTML5, User Interface (UI), Front-end, User Experience (UX), UI Design, Scalability, App Store, Google Play Store, Tailwind CSS, Next.js, RESTFul APIs, Crash Reporting, Amazon Web Services (AWS), React Native Navigation, HTML, General Data Protection Regulation (GDPR), CI/CD Pipelines, Push Notifications, Data Modeling, Database Structure, Scalable Architecture, REST, Back-end, Minimum Viable Product (MVP), GitHub Actions, Web Development, Full-stack, Web Applications, Software Development, Testing, API Development, Application Security, Cloud, Multi-tenant SaaS, Back-end APIs, Rest APi
Front-end Developer
2022 - 2023
Snoop Media
- Developed new features for the React Native mobile app, including a real-time messaging system with a custom bidirectional infinite list and a Netflix-style discovery screen handling large media datasets.
- Optimized the discovery screen rendering large media datasets from 40fps to a stable 60fps, including on low-end devices, and enhanced caching to reduce loading times in the app.
- Integrated new, generic components that are fully customizable, strongly typed, and with tests.
- Developed new features for the dashboard made in React, such as charts using ApexCharts.js to visualize the application metrics and other pages to manage the product.
- Developed a brand new discovery part of the application, organized with tabs containing sections of items, combined with a search area for complementary needs. Worked on maintaining good performances while having to display that amount of data.
- Integrated analytics frameworks such as Firebase Analytics, UX-Cam, and Amplitude.
- Integrated basic mobile application features such as custom in-app notifications, improved performance, and loading time over the application.
- Integrated new, generic components that are fully customizable, strongly typed, and with tests.
Technologies: React Native, TypeScript, Expo, Styled-components, React Apollo, GraphQL, UI Animation, Redux, Context API, Figma, Mobile App Development, Sentry, Responsive, Android, iOS, Clean Architecture, Atomic Design, Mobile Apps, Segment, Firebase Analytics, Amplitude, UXCam, Real-time Data, WebSockets, Docker, Amazon Web Services (AWS), Mobile, ApexCharts.js, React, Web & Mobile Applications, Full-stack Development, Full-stack, Cross-platform, API Integration, App Development, Cross-platform App Development, Mobile Architecture, Jest, Architecture, Mobile Development, User Interface (UI), Front-end, Pixel Perfect, User Experience (UX), Performance Optimization, Query Optimization, Scalability, App Store, Google Play Store, Next.js, NestJS, Analytics, Crash Reporting, Telemetry, React Native Navigation, CSS, General Data Protection Regulation (GDPR), Dashboards, Push Notifications, Scalable Architecture, GitHub Actions, Web Development, Web Applications, Software Development
Mobile Developer
2022 - 2022
sGuiding
- Built a React Native app from scratch in TypeScript, with an interactive Google Maps SDK map surfacing nearby sites and itineraries.
- Developed a step-by-step tour mode that guides users along an itinerary on the map and auto-plays each site's audio on arrival — working in both foreground and background.
- Built an in-app marketplace for purchasing audio tours via in-app purchases.
Technologies: React Native, TypeScript, Redux, Axios, Location Tracking, Audio, Sentry, Google Maps SDK, Mobile App Development, Mobile Apps, Front-end Development, Audio Streaming, Mobile, Cross-platform, API Integration, App Development, REST APIs, Cross-platform App Development, Mobile Architecture, Architecture, Mobile Development, Google Maps, User Interface (UI), Front-end, User Experience (UX), App Store, Google Play Store, RESTFul APIs, Crash Reporting, React Native Navigation, GPS, Push Notifications
Mobile Developer
2022 - 2022
Bloomflow
- Implemented a business card scanner with text recognition using Google's ML Kit.
- Resolved security vulnerabilities across Android and iOS.
- Reworked the UI and navigation flow of multiple screens to add a company and other design updates in the application.
- Maintained and extended the app over multiple engagements.
Technologies: React Native, Redux, Optical Character Recognition (OCR), ML Kit, Sentry, Fastlane, Loopback, JavaScript, Mobile App Development, Mobile Apps, Styled-components, Front-end Development, Mobile, Cross-platform, App Development, REST APIs, Cross-platform App Development, Swift, Mobile Development, User Interface (UI), Front-end, User Experience (UX), Performance Optimization, Query Optimization, App Store, Google Play Store, RESTFul APIs, Crash Reporting, React Native Navigation, IT Security, CI/CD Pipelines, SaaS, QR Codes
Lead Mobile Developer
2020 - 2022
Lanslot
- Led the development and release of the application in stores and designed features with the product owner and lead back-end developer.
- Re-architected real-time voice channels from a P2P mesh to an SFU topology, lifting stable room size past the prior 3–5-user ceiling where the mesh degraded under load.
- Built key features such as voice channels (VoIP with WebRTC), real-time chat (WebSockets), and a dynamic feed leveraging server-side rendering principles.
- Managed and reviewed developers' code and assisted in developing new features.
- Developed a robust architecture with a caching system to share common data between screens and optimized the network calls.
- Created a clean and organized structure for the application with a UI library full of customizable components.
- Developed smooth animations and transitions, running at 60 frames per second on low-end devices.
- Developed end-to-end tests to avoid regression on new releases.
Technologies: React Native, TypeScript, GitLab CI/CD, Firebase, WebRTC, GraphQL, React Apollo, WebSockets, Fastlane, CodePush, Redux, Java, Objective-C, Jira, Adobe Experience Design (XD), Lottie, Mobile App Development, Mobile Apps, E2E Testing, Styled-components, Front-end Development, Mobile, Web & Mobile Applications, Cross-platform, API Integration, App Development, Cross-platform App Development, Mobile Architecture, Jest, APIs, Architecture, Mobile Development, Detox, VoIP, User Interface (UI), Front-end, Pixel Perfect, User Experience (UX), UI Design, Performance Optimization, Query Optimization, Scalability, App Store, Google Play Store, Analytics, Crash Reporting, Telemetry, Amazon Web Services (AWS), React Native Navigation, IT Security, CI/CD Pipelines, Technical Leadership, Dashboards, GPS, Push Notifications, Scalable Architecture, Videos, Software Development, Testing
Web Developer
2020 - 2020
EDGCo
- Developed task organization features, workspaces, and tags for grouping and structuring work.
- Built a calendar view for visualizing and organizing tasks over time.
- Optimized Redux-Saga data flow across the application, reducing unnecessary re-renders and state churn screen by screen.
- Refactored the web app for responsive layouts across screen sizes.
Technologies: React, TypeScript, Redux, Docker, Front-end Development, Web Development, API Integration, App Development, REST APIs, Redux Thunk, HTML5, Front-end, RESTFul APIs, CSS, HTML, General Data Protection Regulation (GDPR), Minimum Viable Product (MVP), Web Applications, Software Development
Full-stack Developer
2019 - 2020
EDGCo
- Built manual trading features spanning multiple exchanges, wallet-to-wallet transfers, and direct buy/sell execution across platforms.
- Developed the bot creation and configuration flow, letting users spin up and deploy new trading bots from the web app.
- Optimized the Node.js market-sync services responsible for keeping price data current across exchanges.
- Built a standalone Node.js notification service with configurable desktop notification settings in the web app.
- Added performance analysis charts and graphs to the web application for tracking trading results.
Technologies: Node.js, React, TypeScript, Docker, Redux, WebSockets, Redis, Full-stack Development, Front-end Development, Back-end Development, Full-stack, API Integration, App Development, APIs, REST APIs, Redux Thunk, Front-end, Express.js, RESTFul APIs, HTML, General Data Protection Regulation (GDPR), Data Modeling, Database Structure, Scalable Architecture, REST, Back-end, Web Development, Web Applications, Software Development, API Development, Cloud, Back-end APIs, Rest APi
Full-stack Developer
2019 - 2019
EDGCo
- Built the whole project end-to-end: a responsive web application where users browse curated outfit styles and customize them before purchase.
- Developed the back-end REST API with Strapi, modeling the product catalog and content over a backing database.
- Implemented the full checkout flow: cart management, Stripe payment processing, and order generation.
Technologies: React, Redux, TypeScript, Node.js, PostgreSQL, Stripe, Docker, Front-end Development, Full-stack Development, Back-end Development, Full-stack, API Integration, App Development, APIs, REST APIs, Stripe Payments, Redux Thunk, Front-end, eCommerce, Express.js, Strapi, CSS, General Data Protection Regulation (GDPR), Stripe Connect, Data Modeling, Database Structure, REST, Back-end, Web Development, Web Applications, Software Development, API Development, Cloud, Back-end APIs, Rest APi
Project History
Career Assistant
RAG-powered CV tailoring and profile summary generation, grounded in verified work history.
I built a full-stack TypeScript application (NestJS and React) that implements a two-stage LLM pipeline: structured job description analysis followed by constrained generation. It uses local embeddings (Ollama and nomic-embed-text) and Qdrant vector search across separate collections for experiences, skills, and writing style.
Anti-hallucination constraints ensure that outputs reference only real data.
It outputs an ATS-optimized CV schema and personalized pitches via the Claude API, with side-by-side variations and keyword-matching diagnostics.
I built a full-stack TypeScript application (NestJS and React) that implements a two-stage LLM pipeline: structured job description analysis followed by constrained generation. It uses local embeddings (Ollama and nomic-embed-text) and Qdrant vector search across separate collections for experiences, skills, and writing style.
Anti-hallucination constraints ensure that outputs reference only real data.
It outputs an ATS-optimized CV schema and personalized pitches via the Claude API, with side-by-side variations and keyword-matching diagnostics.
Emoleaks
Emoleaks is an application to help content producers test their media (such as ads) on groups of testers using AI. On the web application, the tester can watch the content while being analyzed by an AI to detect the emotions felt so that the producer can know if the content creates the desired effect on potential customers before publishing the content. I mainly worked on the API and the web application of the product.
Kleos
Kleos is a fitness application to plan and log your workouts and analyze your progress through your journey. I used this project to learn new skills and try architectures and dependencies.
ACCOMPLISHMENTS
• Designed elegant interfaces on Figma, matching with a theme I created.
• Developed the applications with React Native and Expo.
• Built the application with Watermelon DB (based on SQLite) to store all workout data.
• Developed complex animations and transitions with Reanimated and SKIA.
• Designed the store's pages and descriptions and released the application.
ACCOMPLISHMENTS
• Designed elegant interfaces on Figma, matching with a theme I created.
• Developed the applications with React Native and Expo.
• Built the application with Watermelon DB (based on SQLite) to store all workout data.
• Developed complex animations and transitions with Reanimated and SKIA.
• Designed the store's pages and descriptions and released the application.
Education
2018 - 2020
Dual Master's Degree in Computer Engineering
Beijing Jiaotong University - Beijing, China
2015 - 2020
Dual Master's Degree in Computer Science
Epitech - Paris, France
2015 - 2018
Bachelor's Degree in Computer Science
Epitech - Nantes, France
Skills
Libraries/APIs
Node.js, React, REST APIs, API Development, Back-end APIs, WebRTC, Redux-Saga, Context API, Google Maps, Google Maps SDK, Stripe, Skia, ApexCharts.js, Zod, Drizzle, NativeWind, Claude API, Stripe Connect, WhatsApp API, Telegram Messenger API
Tools
Expo, GitLab, GitHub, Slack, Zsh, Xcode, GitLab CI/CD, React Apollo, Sentry, Figma, Adobe Experience Design (XD), Firebase Analytics, Redux Thunk, Prisma, Claude Code, Jira, Fastlane, Google Places SDK, Amazon Simple Email Service (SES), Auth0, Amazon EKS, RabbitMQ, Shadcn
Languages
JavaScript, TypeScript, CSS, HTML, GraphQL, SQL, HTML5, C, C++, C#, Java, Objective-C, Swift
Frameworks
React Native, Redux, NestJS, Detox, Next.js, Tailwind CSS, Express.js, Loopback, Jest
Paradigms
Cross-platform, App Development, Mobile Development, REST, Testing, E2E Testing, Responsive, UI Design, Microservices, Scrum, Clean Architecture, Mobile App Design
Platforms
MacOS, Firebase, Android, iOS, Visual Studio Code (VS Code), Mobile, Amazon Web Services (AWS), Docker, DigitalOcean, Watermelon AI, Vertex AI, Ollama, Google Cloud Platform (GCP)
Storage
PostgreSQL, Redis, Database Structure, MongoDB, SQLite, Amazon S3 (AWS S3), Datadog, MMKV
Other
Mobile Apps, Styled-components, Mobile App Development, Front-end Development, Web Development, Full-stack Development, Back-end Development, Full-stack, Cross-platform App Development, API Integration, APIs, Front-end, User Experience (UX), RESTFul APIs, Crash Reporting, React Native Navigation, Back-end, French, Web Applications, Software Development, Cloud, Rest APi, Software Architecture, WebSockets, Axios, Apollo, Design, UI Animation, Lottie, Real-time Data, Web & Mobile Applications, Software Engineering, Mobile Architecture, Architecture, VoIP, Deployment, User Interface (UI), Pixel Perfect, eCommerce, Performance Optimization, Query Optimization, Scalability, App Store, Google Play Store, Strapi, Analytics, Telemetry, IT Security, General Data Protection Regulation (GDPR), CI/CD Pipelines, Technical Leadership, Dashboards, GPS, Push Notifications, Data Modeling, Scalable Architecture, SaaS, Minimum Viable Product (MVP), GitHub Actions, Agentic Coding, Application Security, Multi-tenant SaaS, CodePush, Optical Character Recognition (OCR), ML Kit, Location Tracking, Audio, Atomic Design, Segment, Amplitude, UXCam, Audio Streaming, Stripe Payments, Amazon RDS, Vite, EAS, Big Data, Google Cloud ML, AlloyDB, Qdqrant, LLM Integration, RAG Pipelines, Artificial Intelligence (AI), Zustand, AI Agents, Videos, Large Language Models (LLMs), QR Codes, Agentic AI, Payments, Financial Services, Fintech, WhatsApp, Live Chat, Voice Recognition, Webhooks
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