Lukas Klinzing, Developer in Vienna, Austria
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Lukas Klinzing

Verified Expert  in Engineering

Full-stack Developer

Vienna, Austria
Toptal Member Since
March 10, 2022

Lukas is an accomplished full-stack engineer with 16 years of experience developing applications and scalable infrastructures for global startups and big enterprise corporations. His primary focus is on creating exceptional UI-heavy web applications and AI-based software. Lukas has a profound understanding of business requirements and can adeptly turn them into user-friendly solutions. He is committed to continuous self-improvement and supporting colleagues in reaching their full potential.

React, Next.js, Figma, Tailwind CSS, ChatGPT, OpenAI GPT-4 API, Remotion, Auth...
JavaScript, React, TypeScript, Node.js, Monorepos, Figma, System Design...
Cloud Infrastructure, Backbone.js, Continuous Delivery (CD), Figma, JavaScript...




Preferred Environment

Visual Studio Code (VS Code), Docker, Figma, React, TypeScript, NestJS, REST, GraphQL, Firebase, Windows

The most amazing...

...thing I've developed is a high-performance price editing tool for the biggest sports activity platform to maintain thousands of prices of various activities.

Work Experience

Designer | Full-stack Engineer | Architect

2023 - 2023
  • Created a simple and engaging landing page for FocusFlow, a personal habit and activity tracker powered by AI.
  • Leveraged Firebase to complete the MVP project in just two weeks with lightning speed.
  • Built the application using atomic design principles on a robust React UI framework, enabling efficient and consistent development.
Technologies: React, Next.js, Figma, Tailwind CSS, ChatGPT, OpenAI GPT-4 API, Remotion, Auth, Google Cloud, Speech to Text, Speech Recognition, Google Speech API, Generative Pre-trained Transformer 3 (GPT-3), Large Language Models (LLMs), Search, Embedded Systems

Senior Lead Front-end Engineer

2020 - 2022
  • Took ownership of DevOps, E2E testing, TypeScript migration, system design, private package management, and learning sessions.
  • Introduced a TypeScript migration plan and migrated over 50% of code within four months.
  • Established the weekly learning and mobile programming sessions to improve and align on coding style.
  • Reduced user acceptance testing effort by introducing an E2E testing framework and pipeline.
  • Introduced a system design and defined a plan to standardize all significant components in an atomic design style.
  • Rebuilt the complete checkout, including the booking and payment process.
  • Built an advanced price editing tool for defining granular, non-linear prices.
  • Designed an architecture with private package management to combine and reuse cross-application design and functionality.
Technologies: JavaScript, React, TypeScript, Node.js, Monorepos, Figma, System Design, Design Systems, Continuous Delivery (CD), DevOps, CSS, Semantic HTML, Linux, Redux, HTML, Next.js, Git, REST APIs, Amazon Web Services (AWS), Architecture, Cypress, OAuth, JSON Web Tokens (JWT), eCommerce, SQLite, Express.js, Axios, Payment Gateways, Vercel, eCommerce APIs, SDKs, Integration

UX Designer | Senior Full-stack Engineer

2008 - 2020
  • Built a scalable social marketing machine that delivers around one million emails and social network notifications daily.
  • Designed and implemented several custom solutions for a content management system.
  • Built the highly advanced admin user interfaces to manage dynamic content, email marketing campaigns, and email delivery schedule.
  • Migrated multiple projects from JavaScript to TypeScript in a continuous and well-defined migration plan.
  • Established end-to-end tests into existing systems to confidently upgrade to newer solutions.
  • Built the reusable frameworks for smart systems like smart TVs and smart mirrors.
Technologies: Cloud Infrastructure, Backbone.js, Continuous Delivery (CD), Figma, JavaScript, Docker, React, React Native, CSS, TypeScript, Semantic HTML, Serverless, Linux, Full-stack, Redux, MySQL, HTML, APIs, REST APIs, Amazon Web Services (AWS), Architecture, System Architecture, System Architecture Design, Tailwind CSS, Cypress, OAuth, JSON Web Tokens (JWT), Cloud Firestore, eCommerce, Electron, Material UI, SQLite, Express.js, Axios, MongoDB, Payment Gateways, Stripe, Vercel, eCommerce APIs, SDKs, Integration

Smart TV Developer

2011 - 2011
  • Built multiple smart TV apps for a range of companies, including RTVE.
  • Invented a directional layout management system similar to today's well-known Flex system in CSS.
  • Invented a smart TV-based directional navigation and focus system that allowed the automatic focus of elements. It used the directional layout management technique to understand which elements are visually next to each other.
Technologies: JavaScript, Backbone.js, Smart TV, jQuery, Testing, Performance, Optimization, SDKs, Integration

Full-stack Developer

2008 - 2010
  • Co-founded the company with the idea to build an Austrian-wide company network (B2B) which could help connect companies.
  • Designed the system and architecture, based on .NET and ASP.NET Forms and jQuery for the front end.
  • Invented a visual on-page editing content management system which was revolutionary at the time. The website allowed the drag and drop components, written in ASP.NET Form controls into slots.
  • Implemented a back-end system allowing to define content models. This automatically created CRUD pages to create, read, update and delete content.
  • Managed a team of content editors that used my CMS to fill the website with around 200.000 company information from Austria.
Technologies: .NET 3, VB.NET, Forms, ASP.NET, jQuery, SQL, ASP.NET Web Forms, Entity Framework, SQLite, SDKs, Integration

Shopping Cart for Activities and Rental
The company provides services to book ski courses. The requirement was to enable adding rental equipment to the booking. I designed and implemented a shopping cart system, allowing booking activities and rental products.

We ensured everyone understood the customer's purpose and requirements during the discovery phase. After that, the project's planning began, and solutions for the user experience were designed.

In the MVP, we built first a rental addon cart, which allowed the user to add rental equipment to his selected activity.

I rebuilt the checkout from the ground up to support multiple products for the booking, which included customer details, participant information, rental shop pickup selection, and the payment process itself.

Product Management and Price Editing
Sports activities like skiing courses had very individual prices, so a new system for managing those activities on the platform was designed.

The prices depended on start times, group or private lessons, custom duration options, the number of participants, and selected activity durations for each provider.

Each activity provider can manage periods when providing ski course activities within the year. For this, a CRUD application was created.

Each provider can manage their offering, including basic information about the product. Also, each product is enriched with duration options that describe how long a course takes place. The provider can have both private and group offers, usually from several hours to multiple days. For this, a management application was created.

Since the prices depended on many aspects, such as duration option, period, and the number of days or participants, a sophisticated tool was created, allowing granular but efficient price editing. The keyboard navigation was enabled to enhance productivity so that the provider could navigate quickly between all the different prices and surcharges. | Prompt Management and AI Workflows is a powerful engine that executes complex AI tasks in real time. It is built using React, Firebase, and Google Cloud technologies. With, you can create teams and projects for AI-specific tasks in any industry. Like ChatGPT on steroids, it enables you to convert repetitive tasks into single AI Runners. By connecting these runners to Buckets, you can scale AI execution to new heights. | Self-improvement SaaS
This project is based on React, Firebase, and AI. It is designed for individuals who wish to improve themselves by keeping track of their daily activities, reflecting on their progress, and monitoring their habits. React, Tailwind and Firebase were used for quick development, and the MVP was completed in just two weeks.

Email Marketing Management Software

Management suite that maintains hundreds of individual user segments and creates, schedules, and delivers emails.

The marketer can create individual user segments with highly advanced filtering UI. The software can handle hundreds of thousands of users grouped in those segments.

Visual tool to build custom emails with reusable blocks and intuitive variable placement to enable highly individual emails.

The high-performance architecture allows to schedule around 500,000 emails across the day and delivers it to a dispatcher service such as Mandrill or SparkPost.

Advanced tracking of events happening during delivery, opening, and clicking. The system can use analytics to put users into segments so that follow-up emails can be created and the user experiences a highly customized story flow. A dashboard displaying information about segments and campaigns gives insights into the success of the marketing activity.

Fintech Web Scraper and Syncer

A distributed queue-based web scraper and API handler to fetch and collect payment histories, transforming them based on individual criteria and feeding them back into a third-party web service. It can be called on-demand or scheduled periodically via a user interface.

Smart TV App and Framework

At the beginning of the smart TV trend when the TVs were very inefficient, I was hired to build a high-performance application for the smart TV for the Spanish RTVE. At the time, there was also no actual framework for how to layout apps and how to navigate on the screen. Only directional navigation, enter and back keys, and four-color buttons were available.

I designed a layout framework and navigation logic that allowed directional navigation and focused on-screen elements. This framework allowed positioning elements similar to today's CSS flex layout logic. Based on the positioning, the navigation of directional keys could be calculated, and focusing was automated. Before this framework, programmers had difficulty figuring out what element should be focused on after hitting the arrow buttons.

The application had multiple screens. Overview with categories and recently added videos, search screen, a detailed view of a video or a series of videos, and the video player itself.

SaaS for Generating Smart Contracts

Software as a service that allows generating smart contracts based on predefined templates. Users can build and deploy, for example, ERC20 contracts by just filling out a form and hitting a button. The generator is built-in solidity and is a smart contract by itself.

After searching for some solutions, I found one where it is possible to generate and compile smart contracts from within a currently running smart contract. This allowed me to generate smart contracts from within my smart contract.

The SaaS allows authentication of users and subscribing to services. It has a few landing pages, a user area with dashboards, and a small marketplace that allows generating customized smart contracts predefined with some templates.


React, Backbone.js, Node.js, REST APIs, Delayed Job, Stripe, Puppeteer, jQuery, Entity Framework, Web3.js, OpenZeppelin, Auth, Google Speech API, Firebase Web SDK, Google Vision API, SendGrid API


Figma, Git, MetaMask, ChatGPT, Google AI Platform, Zapier, Notion, Spreadsheets, SendinBlue, SendGrid


React Native, Redux, Next.js, Electron, Material UI, Express.js, Svelte, NestJS, Tailwind CSS, Cypress, JSON Web Tokens (JWT), .NET 3, ASP.NET, ASP.NET Web Forms, Jest, Hardhat


TypeScript, PHP, JavaScript, SQL, CSS, HTML, Semantic HTML, GraphQL, Solidity, VB.NET


Continuous Delivery (CD), REST, Testing, DevOps, Automation


Docker, Firebase, Vercel, Linux, Windows, Amazon Web Services (AWS), Ethereum, Visual Studio Code (VS Code)


MySQL, Cloud Firestore, SQLite, Google Cloud, PostgreSQL, MongoDB, Data Validation, Sync


User Experience (UX), Serverless, Monorepos, System Design, Design Systems, Customer Data, Shopping Carts, Full-stack, APIs, Axios, SDKs, Integration, Cloud Infrastructure, SparkPost, Message Queues, Scheduling, Checkout, Payment APIs, Card Payments, Web Crawlers, Web Scraping, SaaS, Fintech, OAuth, Architecture, System Architecture, System Architecture Design, eCommerce, Payment Gateways, eCommerce APIs, Job Schedulers, Videos, Video Players, User Interface (UI), Smart TV, Navigation Design, Performance, Forms, Optimization, Ethers.js, Smart Contracts, Ethereum Smart Contracts, Cryptocurrency Wallets, OpenAI GPT-4 API, Remotion, Speech to Text, Speech Recognition, Generative Pre-trained Transformer 3 (GPT-3), Large Language Models (LLMs), Search, Embedded Systems, OpenAI GPT-3 API, Semantics, Milvus, Generative Pre-trained Transformers (GPT), Pinecone, Framer X, Framer, CSV, CSV Import, CSV Export, API Integration, App Integration, Natural Language Processing (NLP), Spreadsheet Automation, IT Automation, Task Automation, Chakra UI, LangChain, Email Marketing, Email Marketing Automation, Lemon Squeezy, MVP Design, Minimum Viable Product (MVP)

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