Full Stack Engineer with 5+ years building production SaaS on React/Next.js frontends and event-driven GCP backends (Cloud Run, Pub/Sub, GCS, Firebase). I own products end to end, from architecture through deployment in lean, fast-moving teams. Based in Berlin, Chancenkarte holder, available immediately.
Full Stack Engineer with 5+ years building production SaaS on React/Next.js frontends and event-driven GCP backends (Cloud Run, Pub/Sub, GCS, Firebase). At ThatAPICompany, I shipped end-to-end products: TheAuthAPI, a multi-tenant auth platform with real-time key management; The Dog API Middleware, an async image-processing pipeline with retry logic and dead-letter queues; and a production LLM contract-redlining system, plus The Cat API / The Dog API Sites(multilingual marketing site) and two enterprise client APIs (medical imaging parts distributor).
Before that, I worked at GMD on an e-commerce platform, building GraphQL APIs and production Python pipelines in a cross-functional team.
Comfortable owning ambiguous briefs from architecture through deployment in lean, fast-moving teams — the last four years have all been startup/agency environments with no dedicated ops or QA org. LangChainJS open source contributor (PR #7421).
Based in Berlin, Chancenkarte holder. Available immediately for senior full stack and backend roles where I can ship end-to-end.
Languages
Senior Full Stack Software Engineer
Full Stack Software Engineer
Multi-tenant auth SaaS platform
Built multi-tenant auth infrastructure SaaS end-to-end (backend, frontend, SDKs, infra). Handles account hierarchies (multi-tenancy), API key management, rate limiting, and real-time analytics. TypeScript SDKs reduced client integration time by 40%.
Marketing site with interactive API demos
Shipped multilingual (EN/ES) marketing site in SvelteKit with interactive API demos, pricing, signup flow. Implemented i18n with slug-based translation keys for easy content updates. Static generation to Vercel. Adapted design for both cat and dog API branding.
Pet photography session orchestration
Designed and built two decoupled NestJS services orchestrating a multi-stage processing pipeline. First service handles session management, 5-image uploads to GCS, and state persistence. Second service subscribes to Pub/Sub events for async portrait generation and breed analysis. Implemented retry logic with dead letter queue for visibility; status tracking with error messages so failures are diagnosable, not silent.
AI-powered contract analysis
Built LLM contract redlining backend using LangChain + Gemini. Implements RAG with prompt chaining for iterative clause analysis. LangSmith integration for production observability. OnlyOffice loader bug fix merged upstream as LangChainJS PR #7421.
Salesforce integration for order management
Built REST API connecting distributors to Salesforce. CQRS architecture cleanly separates inventory/pricing queries from order creation and tracking. JWT auth via TheAuthAPI. API versioning for multiple customer deployments. GCP Cloud Run with GitHub Actions CI/CD.
Animal API integration service
Service enriches pet photography output with breed data and health tips from TheDogAPI/TheCatAPI. Robust fallback strategies ensure API failures don't degrade user experience. Personalizes results alongside portrait images.
Open source contribution
Fixed OnlyOffice document loader bug in official LangChainJS library. Loader wasn't returning metadata, breaking downstream RAG filtering. Fix was reviewed and merged by maintainers, improving library for all users.
I worked closely with Charef for four years at That API Company and watched him grow from a strong individual contributor into one of our most trusted senior engineers. Over that time, he took on full technical ownership of complex work — on our legal-contract redlining AI project, he owned the scope, stakeholder management, and delivery, moving from executing defined tasks to making the architecture and trade-off decisions the rest of the team depended on. On client work, he operated end-to-end: he led our Salesforce integration from scoping through build, communicating directly with the client throughout. He also raised the bar on code quality across the team and was a genuine mentor — his code reviews made the engineers around him, myself included, better. His seniority is well earned: he handles ambiguity independently and consistently lifts the people around him. I'd gladly work with him again.
I write about systems-level engineering: the kind of implementation details that most tutorials skip over. These are deep dives into topics I found genuinely confusing, written so they don't have to be.
A deep dive into TCP fundamentals and building an HTTP server from scratch, covering the socket layer most engineers never touch.
A production guide to replacing a managed API gateway with a self-hosted Nginx setup: real tradeoffs, config details, and lessons learned.
I am open to senior full stack and backend engineering roles in Berlin and remotely. If you are building something technically interesting and want someone who ships end to end, get in touch.
charafbahria@gmail.com