Théo O.

Senior fullstack developer and founder of ThirdBuild. Directly with my clients (startups, SMEs, project owners), I design and deliver complete web products, from architecture to production, with a real understanding of their business.

I build SaaS platforms, custom ERP and business tools, e-commerce sites, and back-offices, using a modern stack (React, Next.js, TanStack, NestJS, TypeScript, PostgreSQL, Supabase, Stripe). I integrate generative AI and AI agents when the project calls for it (LLM orchestration, automation).

Some delivered products: an ERP for energy brokers (zero re-entry), a digital locker with photo proof and payment, a fully automated training e-commerce platform. Remote, occasional on-site possible in Marseille and surrounding areas.

Technical and product leadership for a fintech startup (Ozapay), as a freelancer: from concept to production. I managed and built the entire product, a multi-token crypto portfolio management mobile application.

Achievements:

Web3 Back-end & API (NestJS + Supabase):

• Custom Web3 API design (auth, tokens, transactions, users)

• Retrieval of balances and historical data per token, price estimation via Pyth oracle

• Cryptocurrency sending with dynamic network fee and nonce management

• Complete metadata integration: name, logo, symbol, decimals, price, variation

• Back-office and application maintenance in PHP / Symfony

Solana Smart Contracts:

• Development and deployment of custom smart contracts (Airdrop, Swap)

• Key security and fine-grained permission management

Flutter Mobile App (iOS & Android):

• Fluid and modern interface: crypto balance, real-time price and variation, transaction tracking (received/sent), filtering by cryptocurrency, and simplified payments

• Enhanced security: protected access to private key and recovery phrase, confirmation screens for sensitive actions

• Profile customization (gallery photo or camera), push notifications via Firebase upon fund receipt

• Global state management with HydratedBloc for optimal performance even offline

Product Roadmap (crypto super app): multi-wallet management, crypto card, IBAN, euro card, integrated swap.

I handle the entire product technical chain: architecture, development, security, mobile, Web3, UX, and agile project management.

Lead fullstack developer through Dev-id (ESN), on over 20 B2B projects for large corporations and scale-ups.

My strength: taking ownership of complex projects from end to end, both on the product and technical sides. I don't just execute specs; I understand the business and user needs before building, then I deliver all the way to production.

On several projects, I played a dual role as developer and Proxy Product Owner: defining requirements, designing architecture, prioritizing, developing, managing delivery, and coordinating teams (up to three teams on a Web3 platform).

Some notable projects, by sector:

• Waste management: a B2B billing engine at the core of the business (calculation, margins, contracts) and an audit module, in React, NestJS, and PostgreSQL

• Aeronautics: for a major industrial group, a Kanban-style innovation portfolio used by 750 employees (with enterprise SSO) and a test bench tool

• Energy: a back-office for tracking energy renovation projects, Python / Django and React, PostgreSQL database

• Travel: an AI-enhanced travel SaaS, launched on iOS and Android, within a B2B travel ecosystem

• Web3 and publishing: a platform for tokenized limited editions, from NestJS backend to smart contracts, IPFS, and mobile applications

Cross-functional stack: React, NestJS, Node.js, TypeScript, PostgreSQL, MongoDB, GraphQL, blockchain integration, testing, and monitoring. Emphasis on quality, performance, and team communication.