
Stefan Tudor Dediu
Verified Expert in Engineering
Software Developer
Bucharest, Romania
Toptal member since July 8, 2021
Stefan has more than 15 years of experience in software development, working in various environments ranging from tech startups to enterprise companies. With expert skills in multiple technologies such as PHP, JavaScript, and Swift, which are his particular strengths, he has focused on building innovative and interesting projects as a freelancer.
Portfolio
Experience
- PHP - 15 years
- Java - 12 years
- Swift - 7 years
- Objective-C - 6 years
- Android - 5 years
- Angular - 4 years
- Node.js - 4 years
- React - 3 years
Preferred Environment
MacOS, PhpStorm, Xcode, Visual Studio Code (VS Code)
The most amazing...
...thing I've accomplished is building TactileImages, a software solution designed to help blind or visually impaired people using AI and machine learning.
Work Experience
Lead Software Developer
Asociatia Pentru Dezvoltare Urbana
- Selected the core technologies, languages, and frameworks fit for all the aspects of the project, responsible for designing the application architecture.
- Managed all aspects of the software development process and coordinated the rest of the team.
- Involved directly in writing the code for several software components of the solution, specifically the mobile, web, and AI.
- Deployed and launched the web and mobile apps on Microsoft Azure and AppStore.
Senior Full-stack Developer, Software Architect
Tei Software Studios
- Developed multiple projects at my consultancy and software development company. I managed a team of 7-10 people, including software developers, graphic designers, and testers.
- Built an online video training platform that enrolled more than a thousand subscriptions and six-digit sales the first week after the launch. It was seamlessly integrated with the existing company's other products.
- Managed the development of the mobile and web applications for a modular, scalable, and integrated IoT platform. The platform was awarded the 2019 Honorable Mention at Microsoft HQ Romania.
Senior Full-stack Developer
MediCircle
- Developed the front end and back end for the MediCircle platform, a platform that facilitates access to cancer treatment and medication.
- Took responsibility for third-party and API integrations: FedEx (address validation, shipping labels generation), Pioneer, Lexicomp, Cypress.
- Implemented the deployment environment and pipelines using AWS services and GitLab CI/CD. The required pipeline passes included Prettier, Lint, and Cypress tests.
Full-stack Developer
Freelance Work
- Created more than six eCommerce stores, helping offline shops expand their businesses online.
- Automated and optimized the back end for an online educational platform for kids improving content management and deployment by over 20%.
- Developed an ERP for a telecommunications company helping them manage their clients, employees, staff, projects, invoices, and reports.
Lead Software Developer
Ipsos Interactive Services SRL
- Managed a team of software developers to create web projects according to custom client specifications.
- Created internal apps and tools, reducing the development time for certain products by more than 30%.
- Contributed to the creation and validation of workflows, procedures, and best practices.
- Developed and successfully launched more than 100 individual projects of different sizes and complexity along with my team.
Experience
TactileImages
https://tactileimages.orgThe platform has a social component — used in schools, it offers visually impaired children the opportunity to study independently. With a mobile app that describes interactive drawings with raised surfaces just like a specialist, they can discover all the things they cannot touch and the world by themselves.
Communications iOS App - VoIP Calls, Messages, and Chat
In addition to development, I designed the mobile app's architecture and acted as product owner for the mobile apps.
Social App for Mentoring Platform
I was the senior iOS developer in charge of the mobile app architecture and development. I used WebRTC to enable audio and video calls and Socket.IO to enable real-time chat conversations between app users.
Social App for Streaming and Video Engagement
The app allowed users to do online viewing sessions on shared content. The sessions could be on the fly or scheduled for later dates and were available to groups of up to eight users.
I oversaw iOS development, implementing new features, maintaining and refactoring code, optimizing app performance, and working with the AWS Chime team.
AI App That Creates Custom Stories for Kids
I designed and implemented the back-end architecture, ensuring efficient communication between the app and the ChatGPT API. This involved creating endpoints to handle user inputs, processing these inputs to generate appropriate prompts for the API, and managing the responses to deliver engaging and coherent stories. Throughout the project, I focused on ensuring the system was scalable, secure, and responsive.
By effectively integrating ChatGPT, we were able to offer a unique and interactive storytelling experience, making the app a valuable tool for parents and an engaging platform for children. This project highlighted my ability to leverage advanced AI technologies to develop practical, user-friendly applications.
Assistant GTP Chat iOS App
My responsibilities spanned both back-end development and the iOS application. On the back-end, I designed and implemented the full Cognito architecture using Node.js and PostgreSQL, including RESTful API endpoints, real-time communication via WebSockets for live conversation presence and messaging, and background job processing for async AI tasks such as email draft generation. I handled user authentication using JWT and Amazon Cognito, and managed deployment and infrastructure on AWS.
A core part of the project was the AI integration: I engineered the system that constructs context-aware prompts enriched with the user's profile, and calls the OpenAI API to generate relevant, actionable insights. The assistant is backed by the OpenAI Assistants API, enabling persistent, context-aware conversations.
Quit Drinking iOS App
My primary responsibility was developing the iOS application and back end using SwiftUI and Node.js, architecting the core features from the ground up — including a 30-day CBT-based challenge system, a daily clarity check-in system, an SOS crisis support modal with guided exercises, and an AI-assisted journaling feature powered by the OpenAI API.
I designed and implemented the journaling feature end-to-end, integrating a large language model (LLM) via the OpenAI API to provide users with personalized, context-aware reflections based on their journal entries, sobriety progress, and emotional check-in data. This involved crafting dynamic prompts that combined user-specific context, such as days sober, recent clarity ratings, and drinking patterns, to generate meaningful, supportive insights rather than generic responses.
Healthcare Logistics Platform
Event Analytics Dashboard
My primary responsibility was designing and building the entire stack, from the back-end infrastructure to the reporting portal. On the back end, I architected a RESTful API with secure authentication layers, JWT for dashboard users, and HMAC-signed requests for mobile clients, as well as a per-project API key system that allows iOS teams to integrate directly without going through the dashboard.
On the front end, I built the reporting portal in React: a full dashboard that presents all tracked data to users, including funnel visualizations, paywall analysis, session stats, and feature usage breakdowns. The portal consumes the API directly and is designed to give both technical and non-technical stakeholders a clear view of how their apps are performing.
Hospital Internal Communications Portal
eCommerce Platform for Personalized Digital Products
I implemented both the front-end (React) and back-end (Node.js) components of the platform, including the checkout workflow and Stripe payment integrations using both redirect-based and embedded solutions. As part of the funnel optimization team, I was actively involved in monitoring and analyzing user behavior across the onboarding and checkout funnels, tracking key metrics such as Conversion Rate and identifying drop-off points. I contributed to conversion rate optimization (CRO) efforts by monitoring, analyzing, proposing, and implementing improvements to the onboarding steps, product customization flow, and checkout experience to increase overall conversions while maintaining a reliable and scalable payment process.
Server-side Rendering Platform for a Computer Games Company
I was part of the team responsible for implementing and automating the full generation pipeline, from back-end content processing to static site creation and deployment. I worked primarily on the back end using Laravel, building the systems that generated the static content and orchestrated the rendering workflow. On the front-end side, I implemented the generated pages using HTML, CSS, and JavaScript to ensure fast load times and search-engine-friendly output. The project focused heavily on server-side rendering, static site generation, and performance optimization to maximize SEO visibility and efficient content delivery.
High-scale Advertising Platform Optimization & Sharding
SSR Learning Platform with Redis Caching (Vue and Laravel)
High-traffic Game Portal Network with Static Generation & Caching
AI-powered Environmental Intelligence Platform
Legal Compliance & Litigation Management Platform for Public Institutions
My responsibilities spanned back-end development and the React front end. On the back end, I designed and implemented the full architecture using Node.js (Express) and PostgreSQL with Sequelize ORM, including RESTful API endpoints, session-based authentication with JWT support, and background job processing powered by BullMQ and Redis for asynchronous tasks such as email notifications and scheduled litigation updates. I managed deployment and infrastructure on AWS, using CloudFormation (SAM) templates to provision VPCs, RDS instances, and S3 buckets, along with AWS SES for transactional email delivery.
A core part of the project was the integration with the Romanian court system (JUST portal), where I engineered SOAP-based XML queries to automatically import and sync litigation case data (including court details, parties, hearing stages, and solutions) on a recurring schedule. The platform also features a robust notification system with MJML email templates, a multi-role access model (Admin, Principal, Secondary users), among others.
Education
Master's Degree in Project Management
University of Economic Sciences Of Bucharest, Faculty of Cybernetics, Statistics and Informatics - Bucharest, Romania
Bachelor's Degree in Computer Science
University Politehnica Of Bucharest - Faculty of Automatic Control and Computer Sciences - Bucharest, Romania
Certifications
Responsive Website Development and Design
University of London | via Coursera
Introduction to Meteor.js Development
University of London | via Coursera
Programming Mobile Applications for Android Handheld Systems
University of Cambridge | via Coursera
Object Oriented Programming in Java
University of London | via Coursera
Certificate in Advanced English
University of Cambridge
Skills
Libraries/APIs
Node.js, React, REST APIs, OpenAI API, Vue, Google Calendar API, Claude API, Stripe, TensorFlow, jQuery, FedEx API, Twilio API, Socket.IO, WebRTC, WhatsApp API, Pandas, NumPy
Tools
Claude, Claude Code, GitHub, PhpStorm, Xcode, SPSS, IBM SPSS, CallKit, Amazon Cognito, ChatGPT, Figma, Amazon Simple Email Service (SES), AWS CloudFormation, Sequelize
Languages
Swift, PHP, HTML, TypeScript, XML, Java, C++, JavaScript, Objective-C, CSS, Python, SQL, CSS2
Frameworks
Laravel, Express.js, Next.js, Angular, CakePHP, Yii, Django, Redux, .NET, Cypress, Core Data, EventKit, JSON Web Tokens (JWT)
Paradigms
API Architecture, Web Application Architecture, Mobile Development, Agile Software Development, Back-end Architecture, Responsive Web Design (RWD), UI Design, REST API Architecture, REST, Application Architecture, Real-time Systems, HIPAA Compliance, Conversion Rate Optimization (CRO), Search Engine Optimization (SEO), Model View ViewModel (MVVM)
Platforms
iOS, MacOS, Visual Studio Code (VS Code), Android, Amazon Web Services (AWS), Google Cloud Platform (GCP), Mobile, Azure
Storage
SlimPHP, PostgreSQL, JSON, Databases, MySQL, Amazon S3 (AWS S3), MongoDB, Redis, Cache, SQLite
Industry Expertise
Healthcare
Other
Artificial Intelligence (AI), English, APIs, Architecture, API Integration, Back-end, Full-stack Development, Technical Leadership, Full-stack, Software Architecture, Startups, Mobile App Development, Mobile Apps, Video Streaming, Third-party APIs, Front-end, Medical Software, WebSockets, AI Integration, Large Language Models (LLMs), Authentication, FastAPI, Back-end Development, AI Design, Web Development, Document Parsing, AI-generated Code, AI Tools, Prompt Engineering, Anthropic, OpenAI, App Store, Push Notifications, Messaging, Minimum Viable Product (MVP), AI Pipeline, Algorithms, Operating Systems, IT Project Management, Web Project Management, Machine Learning, Cloud Architecture, Cross-platform App Development, Microsoft Azure, OpenAI GPT-4 API, Email, Deployment, Supabase, Scalable Architecture, Cloud Infrastructure, Payment APIs, Data Processing Automation, AWS Cloud Architecture, Cursor AI, Conversion Rate, Security, eCommerce, Workflow, Workflow Automation & System Integration, Server-side Rendering (SSR), Static Site Generators, Agentic AI, HIPAA, Healthcare & Insurance, Location Services, Maps, Networks, Calendars, Amazon Chime, Amazon Chime SDK, Portals, Platforms, Healthcare IT, CTO, HeyGen, Database Optimization, Database Table Optimization, Sharding, Performance, Caching, Business Services, Laravel Sanctum, Static Site Development, Infrastructure, Satellite Images, Sentinel 2, Geospatial Data, Geospatial Analytics, Video Processing
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