Florian Ionescu
Verified Expert in Engineering
Full-stack Developer
Kiel, Schleswig-Holstein, Germany
Toptal member since February 23, 2022
Florian is a hands-on fractional CTO and senior full-stack engineer with 12 years of experience taking inherited, messy codebases to production. He manages the entire stack, including React/TypeScript, Node/GraphQL, cloud infrastructure, CI/CD, auth, search, and observability. Most recently, Florian was the sole developer of a finance-recruiting platform, taking inherited code to production. Additionally, he integrated AI, including a Claude-queried MCP server.
Portfolio
Experience
- SQL - 10 years
- Docker - 10 years
- Linux - 10 years
- JavaScript - 10 years
- Node.js - 5 years
- React - 5 years
- TypeScript - 3 years
- Svelte - 1 year
Preferred Environment
Linux, Docker, Node.js, Amazon Web Services (AWS), PostgreSQL, MobX, Full-stack Development, NixOS, Fractional CTO, React
The most amazing...
...thing I've developed from the ground up is my smart home system, including an administrative web app, custom hardware, and AI integration.
Work Experience
Senior Full-stack Software Engineer
David Kim Consulting LLC
- Owned architecture, infrastructure, CI/CD, auth, search, and observability as sole developer of a React 18, TypeScript, Node.js, GraphQL, and PostgreSQL SaaS platform (300+ PRs merged).
- Replaced a search cluster, sync daemon, and cache with plain PostgreSQL search (SQL filters, trigram indexes), shipped with parity checks; deleted around 8,500 lines of infra.
- Migrated a two-repo git-submodule setup into a single monorepo with a one-command Docker dev environment and three-environment (dev/staging/prod) GitHub Actions CI/CD.
- Integrated enterprise SSO (OAuth) and locked the entire GraphQL API to role-based auth after a security review, with subdomain-isolated authentication per portal.
- Built the email system: corporate-mailbox sending via a Graph API (OAuth), send-on-behalf-of, attachments, and pre-send validation.
- Shipped a read-only MCP (Model Context Protocol) server so recruiters can query the platform from an LLM assistant (Claude).
- Instrumented end-to-end observability with OpenTelemetry traces and logs, plus structured error tracking and a local metrics/logs/traces stack/production Posthog setup.
- Reworked back-end testing so each integration test runs in parallel on an isolated template-cloned PostgreSQL database with a Dockerized Playwright end-to-end suite.
Lead Full-stack Software Engineer
Antidefault
- Implemented a multi-tenant system architecture based on Kubernetes to ensure scalability and high availability.
- Designed and animated 2D and 3D front ends for business clients using Tailwind, Three.js, WebGL shaders, GSAP, and SVGs in Inkscape.
- Developed business websites as full-stack SvelteKit/Node.js apps in tight feedback loops with customers using Agile methods.
- Implemented CI/CD pipelines on GitHub to build Docker containers and push them to private container registries.
- Deployed and managed several highly available Kubernetes clusters in production environments using Talos Linux, Ansible, and Terraform.
- Monitored and managed the websites deployed to the Kubernetes clusters, as well as PostgreSQL database instances and other microservices.
- Analyzed risks and implemented prevention and recovery solutions to ensure GDPR compliance and data safety even during disasters.
Senior Full-stack Software Engineer
Tapmax
- Developed a SaaS app according to client specifications, including user registration, QR code management, and administrative features using a modern Svelte (SvelteKit, Node.js, TypeScript/JavaScript), Supabase (PostgreSQL), and Vercel stack.
- Implemented a modern CI/CD process using Docker and GitHub Actions.
- Documented the developed app and its CI/CD process to ensure a smooth transition to other developers.
- Deployed the app via CI/CD to Vercel as a serverless application in both a staging and live environment.
Senior Full-stack Software Engineer
CAI International Inc
- Migrated screens of a macOS app to the web using React and JavaScript.
- Implemented PHP REST API endpoints to connect the screens to the Sybase SQL database.
- Met with stakeholders regularly to ensure alignment between product specs and stakeholder expectations.
- Accompanied the product launch and addressed feature requests and issues as they arose.
Front-end Web Developer
Guild of the ROSE
- Implemented the Big Five psychological evaluation using JavaScript, React, and Next.js, with its result displayed as a radar graph using Nivo.
- Implemented the MetaPrompt tool with JavaScript, React, and Next.js used as a training and productivity tool.
- Set up a reusable development environment with Docker Compose.
Senior Full-stack Software Engineer
Stern & Schatz GmbH
- Developed a new administrative system from the ground up using React and JavaScript to build a single-page application and Laravel and PHP 7 to provide a GraphQL API.
- Migrated the legacy system seamlessly to the new administrative system by utilizing SQL views to integrate the old database while ensuring backward compatibility.
- Integrated Amazon's MWS API to automate the administrative work to keep products and their stock in sync.
- Incorporated the REST API by Mailchimp and the SOAP API by Mediafinanz to send payment warning emails to customers in specific time intervals and send claims to the collection department.
- Led the development of a robust and encrypted backup system that used AES-256 and RSA for encryption.
- Built a React and JavaScript component to track employees working time, vacation, and sick days.
Mid-level Full-stack Software Engineer
Stern & Schatz GmbH
- Set up a reusable development environment with Docker Compose.
- Debugged several emergencies in the live legacy system using jQuery, JavaScript, and PHP.
- Refactored PHP4 code to cut down on maintenance costs, reducing time spent on periodic changes by over 95%.
Junior Full-stack Developer
Stern & Schatz GmbH
- Created a JavaScript webmail client and its PHP API, which most employees now use daily.
- Developed a documentation system with JavaScript and PHP used daily by all employees to organize messages, files, and tasks in threads.
- Implemented bug fixes and features based on assigned tickets.
Experience
Antitether
Smart Home System
The system administration app was built as a React SPA with a PHP back end, providing a REST API. This API was then used by hardware components like lamps, switches, and laser barriers based on the ESP8266 and programmed with Arduino. The hardware was designed in Eagle, soldered together from PCBs and surface-mounted components, and put into 3D-printed cases designed in OpenCAD.
In addition, the system used Raspberry Pis to monitor rooms and detect people, which triggered an event that was used to automatically keep the lights (Philips Hue) on only in rooms with people.
Self-modifying Game Engine
Comparison of Machine Learning Algorithms in the Context of EvoMan
This Python project used four machine learning algorithms, NeuroEvolution of Augmenting Topologies, Deep Q-Network, Advantage Actor-Critic, and REINFORCE, to compare their performance in the context of the open-source game EvoMan. First, the agents were trained against a pre-programmed AI, and then their performance was measured against that AI and against each other.
Udacity Blockchain Capstone Project
Antidefault Virtual Office
Education
Bachelor's Degree in Computer Science
Christian-Albrecht University of Kiel - Kiel, Germany
Certifications
Blockchain Developer | Nanodegree Program
Udacity
Skills
Libraries/APIs
React, REST APIs, jQuery, Node.js, Three.js, API Development, Web3.js, React Testing Library, WebGL, GSAP, OpenAI API, MobX, Socket.IO, Chart.js, Playwright, TensorFlow, Graph API, Stripe, Stripe API, GraphQL API, Leaflet, WebRTC, Apollo Client, SendGrid API, Calendly API, Claude API
Tools
Git, GitHub, JSX, Canvas, Claude, PhpStorm, Docker Compose, LaTeX, GitLab CI/CD, GreenSock, ChatGPT, n8n, Claude Code, Postman, Prisma, Auth0, Amazon Elastic Container Registry (ECR), Amazon Elastic Container Service (ECS), Audacity, Inkscape, Ansible, Terraform, Figma, Knex.js, React Apollo, CircleCI, Amazon OpenSearch, SendGrid, Vitest
Languages
SQL, PHP, JavaScript, CSS, HTML, CSS3, HTML5, PHP 7, TypeScript, ECMAScript (ES6), GraphQL, Solidity, Python, Less, Sass, GLSL, SCSS
Frameworks
Express.js, Tailwind CSS, Truffle, PHPUnit, Material UI, Next.js, Svelte, Bootstrap, JSON Web Tokens (JWT), Laravel, AWS Serverless Application Model (SAM)
Paradigms
Automation, Object-oriented Programming (OOP), REST, Database Design, Web Performance Optimization (WPO), Asynchronous Programming, Test-driven Development (TDD), Component-based Development, Design Patterns, Clean Code, Unit Testing, Responsive Web Design (RWD), Continuous Integration (CI), DevOps, UI Design, UX Design, B2B, Search Engine Optimization (SEO), Testing, Microservices, Scalable Application, Microservices Architecture, Model Context Protocol (MCP), Continuous Delivery (CD), Web UI Design, Web UX Design
Platforms
Docker, LAMP, Linux, Ubuntu, Debian, Blockchain, Arduino, Amazon Web Services (AWS), Vercel, Kubernetes, GreenSock Animation Platform (GSAP), Amazon EC2, AWS Lambda, Calendly, PostHog
Storage
MySQL, Databases, Relational Databases, PostgreSQL, Database Structure, Database Management, Database Architecture, Sybase, Amazon S3 (AWS S3), Elasticsearch, Database Migration, Redis
Industry Expertise
Web Design
Other
Algorithms, Data Structures, Programming, Front-end, Front-end Development, Software Development, APIs, Web Development, Full-stack, Integration, User Interface (UI), Back-end, Dashboards, Back-end Development, Software Architecture, Full-stack Development, MVP Design, CI/CD Pipelines, Web Project Management, Architecture, API Integration, Minimum Viable Product (MVP), Frameworks, Responsiveness, SaaS, User Experience (UX), 3D Animation, Front-end Architecture, Scalability, Static Site Generators, Web Scalability, Lazy Loading, Responsive UI, Third-party APIs, Front-end Design, Documentation, RESTFul APIs, Software Engineering, Data Modeling, Web App Development, Containerization, SDKs, 3D, Software as a Service (SaaS), API Design, Web Application Design, ESP8266, Apollo, Data Visualization, Storybook, Component-based Architecture, Design Principles, eCommerce, Smart Contracts, OpenAI GPT-4 API, OpenAI GPT-3 API, WebSockets, Webhooks, AI Integration, SvelteKit, Hetzner, SVG, General Data Protection Regulation (GDPR), Shaders, CTO, Vector Graphics, Data Privacy, Large Language Models (LLMs), Cryptocurrency, OpenAI, Prompt Engineering, Artificial Intelligence (AI), Code Review, GitHub Actions, System Architecture, Web Animation, Animation, UI Animation, Server-side Rendering (SSR), Application State Management, Core Web Vitals, Accessibility, Startups, Web Accessibility, AI Chatbots, Chatbots, Technical Leadership, Compliance, Data Security, Responsive Web Apps, Vite, CRM APIs, Cloud Infrastructure, Infrastructure, Web UI, Web UX, Real-time Data, Cloud, 3D Modeling, Security, Video Streaming, Agentic Coding, Systems Design, LLM Integration, Email Automation, Multi-tenant Architecture, Multi-tenant SaaS, Early-stage Startups, Machine Learning, LangChain, QR Codes, Supabase, Serverless, OpenStreetMap, Design, Website Design, Web3, 3D Graphics, Computer Graphics, A11Y, Amazon RDS, ECS, Streaming, Apollo Server, PgSync, Infrastructure as Code (IaC), Cursor AI, Single Sign-on (SSO), Application Modernization, Legacy Software, Observability, Telemetry, Monorepos, Migration, NixOS, Fractional CTO
How to Work with Toptal
Toptal matches you directly with global industry experts from our network in hours—not weeks or months.
Share your needs
Choose your talent
Start your risk-free talent trial
Top talent is in high demand.
Start hiring