Oliver Ullman, Developer in Boulder, CO, United States
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Oliver Ullman

Verified Expert  in Engineering

Full-stack Developer

Boulder, CO, United States
Toptal Member Since
April 21, 2021

Oliver is a React expert who has worked with high-profile clients such as Facebook, Chess.com, and Diem and a full-stack developer who brings energy and intelligence to any team he joins. Oliver's clients value his rapid pace of development and high throughput. His love of programming comes from writing clean, elegant, and scalable solutions.


Dfuzr Industries
React, Gatsby, Docusaurus, GraphQL, PHP, WordPress...
React, Gatsby, WordPress, PHP, CSS-in-JS, A/B Testing
React, GraphQL, Relay, PHP, Mercurial, CSS, JavaScript




Preferred Environment

React, Node.js, Jamstack, TypeScript, Gatsby, GraphQL

The most amazing...

...thing I've built is a bot that automatically searched for and applied to jobs with a customized cover letter based on the job, making the process a lot easier!

Work Experience

Senior Full-stack Engineer

2020 - PRESENT
Dfuzr Industries
  • Re-architected Diem.com's background to decouple the front end and back end, eventually using WordPress as a headless CMS with Gatsby and Sass on the front end.
  • Served as the lead developer on Facebook Open Source's showcase site, built with TypeScript, React, Storybook, Sass modules, Jest, Plop.js, and Docusaurus.
  • Used PHP to build a recursive migrator for moving data from Fieldmanager to Advanced Custom Fields for Diem.com.
  • Communicated effectively in a fully remote environment.
Technologies: React, Gatsby, Docusaurus, GraphQL, PHP, WordPress, Advanced Custom Fields (ACF), NPM, SCSS, Webpack

Full-stack Developer

2018 - 2018
  • Implemented site speed optimizations on our WordPress site. I used Lighthouse and GTMetrics to understand what our bottlenecks were, then used preloading, pre-connecting, and critical style inlining to speed up loading by 25%.
  • Developed and maintained the front-end components such as a new universal navigation bar, footer, and consultation form on both of our websites. The first one was our main website, built with React, Gatsby, and SCSS. The second was a WordPress blog.
  • Refactored our styles to be component scoped to better encapsulate our styling. This resulted in fewer errors when writing SCSS and a faster development time.
Technologies: React, Gatsby, WordPress, PHP, CSS-in-JS, A/B Testing

Contract Enterprise Engineer (Full-stack)

2017 - 2018
  • Wrote front-end components with React, Relay, and GraphQL.
  • Created a notification system for order transactions in PHP on the back end. Notifications would be sent out through email and the Facebook app. The challenge here was understanding Facebook's architecture and how to plug into it.
  • Connected to Facebook's address doctor library to implement back-end address validation.
Technologies: React, GraphQL, Relay, PHP, Mercurial, CSS, JavaScript

Full-stack Developer

2017 - 2017
  • Wrote components with Vue.js, VueX (similar to Redux), and SCSS. I also wrote back-end routing using PHP Symfony.
  • Developed a fast, spontaneous algorithmic chess position generator in JavaScript that saved our company the time to create them manually.
  • Developed the entire application (the mini-game solo chess) myself, demonstrating my seniority and planning skills.
  • Contributed to and worked with an 80,000 file codebase. Chess.com is one of the 1000 most popular sites in the world, so it operates on a very large scale.
Technologies: JavaScript, Vue, Sass, Symfony, PHP, CSS, Git

Front-end Developer | Designer

2016 - 2017
  • Used JavaScript, jQuery, CSS, and HTML to create mobile-friendly websites for companies such as Bowtie, Crudex, and The Naiive.
  • Crafted personalized designs using Balsamiq and Photoshop. My time designing websites gave me an appreciation for the importance of visual detail and user experience.
  • Used Jekyll, Lunr, and Bowtie.io to create a fashion blog. This unconventional approach allowed us to have the benefits and security of a static site generator (Jekyll) with the features of a more traditional site such as login and search.
Technologies: JavaScript, CSS, Jekyll, jQuery

Diem Showcase Site

Refactored and maintained Gatsby and React on the front end, using WordPress as a headless CMS. The original setup involved generating a Gatsby build and then translating the built code to PHP to serve using WordPress.

The refactoring involved delegating WordPress to the role of a headless CMS, keeping the Gatsby build instead of translating it, and having the site served up as a static site that is rebuilt upon update using a concurrent Netlify build. I wrote a custom PHP migrator to change our data from Fieldmanager to Advanced Custom Fields.

Facebook Shop

• Built the front-end components with React, Relay, and GraphQL. My work includes the entire account page, the orders page, and parts of the checkout process.
• Created notification system for order transactions in Hack, in-house version of PHP. Notifications are sent out through email and the Facebook app.
• Improved data verification for customer support case assignments on the back end.

Solo Chess

The game consists of mini puzzles that need to be solved, progressively getting more complex. In addition to building the aspects of the application that you can see, I developed a fast, spontaneous algorithmic position generator that saved our company the time needed to create solutions manually.

Diem DIP Documentation

One of the two websites I built that is a part of Diem's documentation ecosystem. This site showcases different proposals that change the way the Diem is run.

It is a static site built with Docusaurus. I used React, Docusaurus, and CSS modules.

Software Engineering Immersive

Hack Reactor


Front-end Web Development



React, Node.js, jQuery, REST APIs, Vue, Backbone.js


GitHub, Create React App, Webpack, Advanced Custom Fields (ACF), NPM, Jekyll, Mercurial, Git, Knex.js


Vanilla JS, Express.js, Symfony, Relay, Jest, Angular, Next.js, Redux


CSS, JavaScript, HTML, Sass, PHP, TypeScript, GraphQL, SQL, SCSS


Jamstack, REST, Design Patterns, Microservices, Unit Testing, Web Architecture


WordPress, Docker, Heroku


MongoDB, MySQL, PostgreSQL


Gatsby, Algorithms, Docusaurus, Full-stack, APIs, CSS-in-JS, A/B Testing, Data Structures

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