API Integration Developer and API Customer Support API Integration Developer and API Customer Support, currently deepening Elixir/Phoenix skills through open source contributions and building multi-tenant SaaS products.

3 years debugging API integrations at Sellsy (3000+ issues resolved, 15 tickets/day, 98% customer satisfaction). Three years spent supporting API integrations at Sellsy have taught me one thing: most integration failures are predictable, optimizable, and avoidable. I am now ready to move from debugging other people's integrations to creating my own. I develop API integrations and connectors, and I share what I learn.

• API Integration: REST APIs, OAuth, Webhooks
• Languages: Elixir, Node.js, Python, JavaScript
• Tools: Postman, Make, n8n,ActivePieces, Git, Docker

• elixir (the Elixir language itself, maintained by José Valim)
  • Fixed misleading IO.read/2 documentation (#15549)
  • Tightened Enum.chunk_while/4 return type spec from Enumerable.t() to [chunk] to match implementation and docs (#15552)
• postgrex (Elixir/PostgreSQL driver, maintained by José Valim) — clarified Duration/interval decoding behavior in docs (#779)
• cfonb (Ruby, Pennylane) — fixed silent line-dropping bug in bank statement parser

Sellsy (Feb 2022 - Present)

API Technical Support (2023 - Present)

• Support developers integrating with Sellsy API (15+ tickets/day, 3000+/year)
• Average staff satisfaction rate: 98% customer satisfaction
• Chift connector support (accounting tools connection)
• Key accomplishments: Identification and documentation of undocumented API V1 models. Contribution to more comprehensive and clearer FAQs. 20% reduction in recurring issues thanks to improved documentation and time savings in customer responses, e.g., the FAQ explaining how to make a V1 call using OAuth V2 is the most frequently used.

Software Developer (Feb 2022 - 2023)

• Backend/Frontend debugging (PHP, JavaScript, jQuery, XSL)
• Feature development (frontend)
• Legacy code maintenance and refactoring
• Developer integration import platform flatfile

Elixir library for parsing French CFONB bank files (relevés de compte) — the first of its kind in the Elixir ecosystem.

• CFONB 120 statement parsing, amounts as Decimal (no float money)
• Published on Hex (v0.1.0)
• Roadmap: CFONB 240, SEPA generation

Unit testing an API in Elixir: useful for showcasing your skills in integration, business testing, and Elixir in an API/B2B context — worth mentioning if you want to demonstrate your expertise in API robustness/back-testing.

A super-fast Node.js microservice based on Fastify that listens to webhooks and pushes them into a Redis queue (via BullMQ) for asynchronous processing.

A concrete example of using the new Make module, which allows the use of JavaScript code. Here, filtering the sales lines of a Sellsy document get by API V2 to create a child document.

Another repository related to Sellsy: example of using Activepieces automation. This feature is not yet available in Sellsy but is coming soon.

APIs: REST, OAuth, Webhooks
Languages: Elixir, Node.js, Python, JavaScript
Tools: Git, Docker, Make/n8n/ActivePieces, Ngrok Databases: PostgreSQL

(+15 years coding across 10+ languages)

• 275+ hours of technical training completed (Dyma Academy)
• 8 professional certifications: Git, Python, Linux/Bash, Docker

• 🔗 GitHub: @nseaSeb
• 🌍 Location: Trizay, Nouvelle-Aquitaine, France 🇫🇷

• ElixirPhoenixRessources: Curated Elixir/Phoenix resources (French)
• clientsetchatiments: CSV/XLS manipulation tools in Python
• english_py:Python script for my own use that I am happy to share. Enables voice output of classic English phrases and voice recognition for pronunciation practice.