Natural-language assistant
Claude API · SQLUsers ask a question in plain language and instantly get the right table or chart, without writing code or knowing how the data is structured.
$ whoami
William Balance
Forward Deployed Engineer · AI, automation & integration
available · full-time · Seoul or remote · no visa sponsorship needed
I work closely with the teams behind a business process, learn how it really runs, then ship the AI that automates it into production: agents, chatbots, code generation and translation. Senior full-stack engineer, 10 years on TypeScript, React, Node.js and AWS, used to high-traffic systems, from back end to mobile.
- 10 years of experience
- 830k+ registrations handled
- €7.5M invoiced through Gayakoa
- 440+ API routes in production
01 — Skills
What I can build
Each skill is described from the user's side. The demos play on their own; click a skill to open it.
Artificial intelligence
Product & platform
Mobile & apps
Reliability & security
Chatbot connected to your data
LLM · permissionsA conversational assistant that answers from your own data, produces shareable reports and respects each person's access rights.
Automatic multilingual translation
LLMAll content translated on the fly into several languages, with no manual work and no files to manage.
Charts generated on the fly
HTML generationVisualizations created automatically from a simple request in plain language.
Face recognition in photos
AWS RekognitionAutomatically find a person among tens of thousands of event photos.
Automating repetitive tasks
AI agentsManual, time-consuming tasks run automatically by AI agents.
Online payments & ticketing
Stripe · SumUpTicket sales with 6 payment methods, real-time quotas and promo codes. Over €7.5M invoiced.
Automatic invoicing
PDF generationInvoices generated and sent automatically: over 42,000 issued with no manual work.
Live events
streaming · WebSocketLive video streaming, chat, polls, gamification and audience voting by text message.
Email & SMS notifications
Mailjet · BrevoCampaigns, confirmations and automatic reminders: over 500,000 emails and texts sent.
Maps & geolocation
Leaflet · MapsInteractive maps to locate venues, events and points of interest.
Branded spaces (white-label)
multi-tenantEach client gets its own branded space, fully isolated and secure.
iOS & Android apps
React NativeComplete mobile apps, built in React Native and published on the App Store.
Games & 3D experiences
Three.js · WebGLA smooth 3D mini flight simulator, playable right inside a mobile app.
Subscriptions & in-app purchases
RevenueCatSubscriptions and in-app purchases to monetize an app simply.
Automated store releases
App Store Connect APIIn-app purchases, listing, descriptions, screenshots and submission sent to the App Store automatically through its API.
Security & access control
multi-tenantFine-grained role-based permissions, protection against unauthorized access and alerts on anomalies.
Scaling under load
AWS serverlessSystems built for heavy traffic: over 830,000 registrations handled smoothly, up to 26,000 on a single event.
Testing & quality
Jest · PlaywrightAutomated tests that secure every release and cover the critical user paths.
demos play on their own · hover to pause
02 — Projects
What I have built
Gayakoa
Multi-tenant SaaS for ticketing and event management (in-person, online, hybrid), where I am the only engineer. Serverless AWS architecture, 440+ API routes, AI in production, real-time live features.
- 725 events
- 830k+ registrations
- €7.5M invoiced
Used by
- Dior
- John Deere
- Intermarché
- Crédit Agricole
- Comexposium (SIAL)
- French Football Federation
Live product
Passing Line
Prep for US teacher-certification exams, on the web (the iOS app is in review). 3,400+ questions written, then cross-checked by an LLM pipeline I designed.
Visit the site
Internal tool
Loop
Coding-agent pipeline: every task goes through development, tests and a check in a real browser, then human validation.
Internal tool
Ads Pilot
Runs the Apple Ads campaigns of my apps without Apple’s console: bids, keywords, budgets and alerts.
Internal tool
LaunchKit
Ships my apps to the App Store through its API: in-app purchases, RevenueCat, listing, screenshots and submission. 10+ submissions.
Freelance missions · 2018 → 2023
- Professeur Caché React · Node · AWS
- YouWho React Native · Neptune
- Galilée Node · AWS · SQL
- Job Connexion Node · MySQL
- Ideel React
- Wazza React
03 — Background
Résumé
-
Dec 2018 → now
Senior full-stack engineer · sole engineer
Gayakoa
Multi-tenant SaaS for ticketing and events. Serverless AWS architecture (440+ API routes), AI in production, real-time live features, multi-tenant security, CI/CD.
-
Jun 2026 → now
Own products
Built alone, with AI agents
PhotoNeat, SkyHaul and BreathCove on the App Store, Passing Line, and Loop, the tool that runs my coding agents. Internal tools: Ads Pilot, LaunchKit.
-
2018 → 2023
Freelance missions
Startups and other clients
Web and mobile development: Professeur Caché, YouWho, Galilée, Job Connexion, Ideel, Wazza.
-
2016 → 2018
Full-stack developer
AT Internet · digital analytics
Security and access-rights team: product protection and permission management. Major migration from AngularJS / C# / Kubernetes to React, Node.js, AWS.
Education
Master's-level qualification (RNCP 7) · IT and information systems
Ynov Bordeaux · 2014–2019
Languages
- French native
- English TOEIC 920
- Korean learning
Other
Private pilot licence (PPL)
$ ./contact --book-call
Let's talk
Book a call: a full-time forward deployed engineer role, an AI project, or full-stack help on a high-traffic system.
A project?
Hiring?
Download my CV (PDF)