CJ Visser, Developer in Saint Ive, United Kingdom
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CJ Visser

Verified Expert  in Engineering

Web Development Developer

Saint Ive, United Kingdom
Toptal Member Since
July 5, 2018

CJ is a seasoned full-stack engineer with nine years of professional experience. Throughout his tenure, he's managed multiple teams and founded several companies. From the financial sector to the entertainment industry, CJ has created products that have gone into the hands of millions of satisfied customers. He excels at cultivating a positive work atmosphere, leading people, designing systems, and tackling problems. What sets CJ apart is his ability to get things done.


OpenAI GPT-4 API, ChatGPT, Messaging, C#.NET, React, TypeScript...
Bluebird Development
API Architecture, React Native, Python, ASP.NET, SQL, TypeScript, Redux, CSS...
ARCx Labs Pty Ltd
React, Next.js, JavaScript, TypeScript, D3.js, Tailwind CSS, BigTable...




Preferred Environment

TypeScript, Node.js, JavaScript, C#, Full-stack, React, Visual Studio Code (VS Code), Web Development, .NET, Data Visualization

The most amazing...

...professional achievement of mine was building a successful software development business during the tough times of COVID-19 without ever missing payroll.

Work Experience

AI Developer (Contract)

2023 - PRESENT
  • Developed a financial advisor AI bot that answers questions based on proprietary knowledge.
  • Built an admin interface to set up various bases, each with its own datasets (vector stores), settings, prompts, and tools (to connect to live, proprietary functions).
  • Developed a testing environment where the bot is trained to pass various South African financial advisor regulatory examinations.
Technologies: OpenAI GPT-4 API, ChatGPT, Messaging, C#.NET, React, TypeScript, Proof of Concept (POC)

Founder and Developer

2018 - PRESENT
Bluebird Development
  • Founded a boutique software development agency specializing in tailor-made software solutions for international clients. Managed a remote team of around 20 people across six countries. Grew the company by 100% year over year.
  • Architected a robust logistics system for Raubex, South Africa's largest construction company. Built on .NET and hosted on Azure on-premises, it still forms a core part of the company's operations.
  • Served as the lead consultant on the Revio payment platform, Reviopay.com. A .NET platform hosted on AWS and integrated with 30+ payment providers and Customer.io. Consulted on the overall architecture and provided code reviews.
  • Architected and led the web development of a new startup in the healthcare industry in Germany, Doctorly.de. Grew from 0 to 50,000 patients during my tenure.
Technologies: API Architecture, React Native, Python, ASP.NET, SQL, TypeScript, Redux, CSS, Node.js, JavaScript, Full-stack, Microsoft SQL Server, MongoDB, Heroku, C#, Vue, React, Web Development, .NET, Data Visualization, Management, Low Code, APIs, Web Accessibility, Team Leadership, API Design, Software Architecture, Technical Leadership, Firebase, Storybook, Remote Team Leadership, Front-end Architecture, Front-end, Single Sign-on (SSO), Styled-components, Automated Testing, OAuth, Agile, Contentful, Design, UX Design, Web Design, UI Design, Amazon Web Services (AWS), NoSQL, AWS Amplify, Amazon DynamoDB, Asynchronous Programming, Proof of Concept (POC), Nuxt.js, PostgreSQL, SQLite

Front-end Developer

2023 - 2023
ARCx Labs Pty Ltd
  • Optimized a Next.js analytics web portal by eliminating duplicate API calls, implementing caching, and optimizing queries. Reduced average page load time from 20 seconds to 3 seconds.
  • Implemented a custom ORM solution to inject variables from the UI into Bigtable queries to transact with a > 400-gigabyte database efficiently.
  • Implemented Storybook and unified all the components to create a one-stop environment for businesses and designers to validate development and track progress.
Technologies: React, Next.js, JavaScript, TypeScript, D3.js, Tailwind CSS, BigTable, Asynchronous Programming


2022 - 2023
  • Constructed and deployed an insight crowdsourcing platform that digitally connects target audiences to a client's brand, leveraging WhatsApp, social media, and AI. The platform is currently used by multiple telco companies and race event organizers.
  • Built the entire framework using .NET, C#, and Azure with dozens of 3rd-party integrations, including payment gateways, ID verifications, location services, etc.
  • Pioneered all technical operations focusing on compliance regulations and data security (ISO 27001, POPI, and GDPR) regarding the customer's personal data.
  • Developed a solution to handle generic plug-and-play requirements and allow for customizable, single-tenanted solutions for institutional clients.
Technologies: .NET Core, C#, Next.js, TypeScript, Azure, Azure DevOps, SQL, Node.js, Verification, Maps, Payment APIs, TensorFlow, Chatbots, Remote Team Leadership, Front-end Architecture, Front-end, OAuth, Agile, Design, UX Design, Web Design, UI Design, Asynchronous Programming, Proof of Concept (POC)


2022 - 2023
Craft Financial
  • Architected and led a team of developers to build a platform for South African freelancers to manage and send quotes and invoices. Created with React, TypeScript, .NET, and C# and hosted on AWS.
  • Laid the groundwork for future product expansion, including internationalization, payment reconciliation, automatic transaction categorization, and integration into an insurance API—to allow free cover on invoices).
  • Integrated into 22seven.com, enabling freelancers to access their business bank account to allow for light accounting—similar to Xero and QuickBooks.
Technologies: Agile Software Development, Architecture, ASP.NET, Azure, Azure DevOps, C#, React, Tailwind CSS, SQL, CI/CD Pipelines, Figma, Full-stack, JavaScript, Web Development, TypeScript, .NET, Data Visualization, Management, APIs, Team Leadership, Low Code, Software Architecture, Technical Leadership, Storybook, Remote Team Leadership, Front-end Architecture, Front-end, OAuth, Agile, Finance, Design, UX Design, Web Design, UI Design, Asynchronous Programming

Lead Developer

2019 - 2023
Tweak Carbon
  • Architected a dynamic quiz solution across the system to enable a carbon scoring system based on users' daily habits and routines.
  • Maintained the Angular and Python app with a team of three developers before rewriting it with .NET, C#, CosmosDB, and React and hosting on Azure.
  • Created a white-label solution for companies to provide internal carbon scoring for their employees. Two of South Africa's most prominent firms, including Spar and Investec, use the solution.
Technologies: Angular, C#, React, Azure, Azure DevOps, Figma, Online Banking, Consumer Insights, Python, Management, APIs, Web Accessibility, Technical Architecture, Full-stack Development, Technical Leadership, Remote Team Leadership, Front-end Architecture, Front-end, Automated Testing, OAuth, Agile, UX Design, Web Design, UI Design, TypeScript, NoSQL, Asynchronous Programming

Front-end Engineer

2020 - 2022
Large CPG Company
  • Worked for a top consumer food company and led the charting/graphing development on the internal UI systems for the sales and marketing teams using D3.js and other tools.
  • Championed the move to update many front-end projects to modern alternatives without security vulnerabilities. Worked through 1,000+ packages to update projects up to a year old.
  • Incorporated various standards and tools to provide a developer-friendly, industry-standard codebase and environment. Added the correct TypeScript checking, linting, code coverage tests, and standardization of code styles.
Technologies: JavaScript, D3.js, TypeScript, React, Jest, Apollo, Jira, GitHub, Jenkins, eCommerce, eCommerce UI, Storybook, Front-end, Styled-components, Automated Testing, UX Design, Web Design, UI Design, GraphQL, Asynchronous Programming

Lead Development Consultant

2018 - 2020
  • Consulted on the BankTech API, an open banking API made with .NET, C#, and Azure. Worked on banking integrations which had to process over five million debit order transactions in one billing run while still using a legacy "flat-file" system.
  • Developed an automated messaging system utilizing WhatsApp for businesses to allow customers of major banks and insurance companies in South Africa to manage their debit orders easily.
  • Built a JavaScript plugin to allow vendors to embed a BankTech payment screen in a website's flow.
Technologies: API Architecture, ASP.NET, SQL, Redux, CSS, JavaScript, Full-stack, Jamstack, React Native, MongoDB, Heroku, Vue, Node.js, React, C#, Web Development, TypeScript, .NET, Data Visualization, Management, APIs, Blockchain, Cypress, Storybook, Front-end, Finance, UX Design, Web Design, UI Design, Asynchronous Programming

Co-founder and Lead Developer

2017 - 2019
  • Co-founded In-House, a startup based in New York that strives to anonymously rate a business on its ESG scores. Built on .NET and React by a team of developers from around the world.
  • Took over an old and defunct system and repurposed it to align with our requirements and modern standards. Introduced many features, including CI, testing, code-first database generation, migrations, etc.
  • Designed, documented, implemented, and shared the technical roadmap up to release.
Technologies: API Architecture, ASP.NET, SQL, Redux, Node.js, JavaScript, Full-stack, Microsoft SQL Server, TFS, Azure, C#, CSS, HTML, React, Web Development, TypeScript, .NET, Management, Front-end, UX Design, UI Design, NoSQL, Asynchronous Programming

Senior Web Developer

2017 - 2018
  • Led the web development for 22seven, a personal budgeting and finance insights application aggregating a user's personal finance. The company integrates with over 100 banks and financial institutions and has a user base of more than 300,000.
  • Improved the aggregate service, where only the latest information was routinely received from the server, like a user's latest bank transactions, and merged with the client-side data.
  • Headed the prototyping of all the new features used by all the platforms—Android, iOS, and web.
  • Pioneered the migration from Angular to React. It was done in an iterative manner, where Angular components were replaced by React components, one by one.
Technologies: React Native, Redux, MongoDB, C#, CSS, HTML, JavaScript, React, Angular, Web Development, TypeScript, Data Visualization, Management, Data Scraping, Data Science, Amazon Web Services (AWS), Front-end, Asynchronous Programming

Senior Software Developer

2016 - 2017
  • Contributed to various back-end solutions that provided content to the apps of South Africa's largest insurance companies—Liberty and Old Mutual. Created on a proprietary UI builder built in .NET and C#.
  • Introduced, developed, and maintained a centralized web console that managed the company's internal systems used by the support personnel, developers, and managers.
  • Implemented the Old Mutual Wine Awards app, a solution where all the users get notified of the winners of the annual wine awards.
Technologies: D3.js, SQL, Redux, Vue, Full-stack, CSS, HTML, JavaScript, Microsoft SQL Server, ASP.NET, C#, React, Web Development, .NET, Mobile App Development, Material UI, Front-end

MES Developer

2014 - 2016
Omnia Fertilizer
  • Created a factory standby and log sheet capturing application used by 1,000+ standby workers and managers of the chemical plants.
  • Developed a dynamic charting web application to represent millions of real-time data points in the plants.
  • Created a near-hit web application that replaced the paper system where 100+ incidents needed to be processed by hand per week.
  • Developed an automated tool that moved 20+ years of confidential Labware data from Lotus Notes, MS Access, and Excel to a centralized SQL Server database integrated into SharePoint.
Technologies: SQL, Full-stack, Visual Basic, CSS, HTML, JavaScript, Microsoft SQL Server, ASP.NET, Python, C#, Web Development, .NET, Data Visualization, Management, Manufacturing Execution Systems (MES), Front-end


I developed LayUp's online web application, a major lay-buy financing eCommerce platform in South Africa. The PWA was made with Vue and TypeScript, with the back end made with TypeScript, Koa, MongoDB, AWS, and CircleCI.

Vehicle Detection

An exciting project as part of Udacity's self-driving car nanodegree program. The program analyzes a video to detect where other vehicles appear. This functionality is foundational for self-driving cars. It involved sophisticated image processing and machine learning.

Old Mutual Wine Show App

I developed the mobile content for South Africa's premier wine show. It was an extremely confidential process involving wine experts. The users of the Old Mutual app, South Africa's largest insurer, received notifications of the wine winners.

Curve Engine

I designed a web application that replaced the current spreadsheet system to calculate and visualize complex pump engineering curves, adjust various calculations, and generate appropriate quotes for their customers. Extensive math and fluid dynamics were used in this project.
2017 - 2018

Nanodegree in Self Driving Car

Udacity - Remote

2012 - 2014

Bachelor's Degree in Computer Science and Mathematics

North West University - Potchefstroom, South Africa

2011 - 2012

Freshman Program in Science

McGill University - Montreal, Canada


React, Vue, Node.js, REST APIs, jQuery, D3.js, TensorFlow, AWS Amplify


Webpack, Git, Figma, Jira, GitHub, Auth0, ChatGPT, TFS, Jenkins, Astro


.NET, Express.js, Redux, Tailwind CSS, Next.js, .NET Core, ASP.NET, React Native, Flask, Jest, Material UI, Nuxt.js, Angular, Cypress


Functional Programming, Management, API Architecture, Web Architecture, REST, Agile Software Development, Test-driven Development (TDD), Azure DevOps, Continuous Delivery (CD), Continuous Integration (CI), Data Science, Responsive Layout, Agile, UX Design, UI Design, Asynchronous Programming, Jamstack, Search Engine Optimization (SEO), Automated Testing


C#, HTML, CSS, JavaScript, SCSS, TypeScript, Visual Basic, Java, C++, Python, GraphQL, Scala, SQL, C#.NET, Elixir, Elm, Clojure


Windows, Visual Studio Code (VS Code), Heroku, Netlify, Linux, Azure, Amazon Web Services (AWS), Firebase, MacOS, Blockchain, AWS Lambda, Shopify, Contentful


MongoDB, Microsoft SQL Server, PostgreSQL, SQLite, NoSQL, Amazon DynamoDB, BigTable

Industry Expertise

Web Design


Data Visualization, Web Development, Full-stack, Freelancing, Gatsby, User Experience (UX), Architecture, Front-end Development, APIs, API Design, Technical Architecture, Full-stack Development, Front-end, Software Development Management, Remote Team Leadership, Front-end Architecture, Proof of Concept (POC), Product Management, Apollo, User Interface (UI), Progressive Web Applications (PWA), CI/CD Pipelines, Online Banking, Consumer Insights, eCommerce, eCommerce UI, Mobile App Development, Low Code, WebSockets, Single Sign-on (SSO), Storybook, Artificial Intelligence (AI), Styled-components, Design, OpenAI GPT-4 API, Lunacy, Machine Learning, Web Accessibility, Team Leadership, Data Scraping, Software Architecture, Technical Leadership, Verification, Maps, Payment APIs, Chatbots, Manufacturing Execution Systems (MES), HubSpot CRM, OAuth, Finance, Messaging

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