David Rottemberg, Developer in New York, NY, United States
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David Rottemberg

Verified Expert  in Engineering

Back-end Developer

New York, NY, United States
Toptal Member Since
October 19, 2021

David has spent the last ten years running startups and acting as the CTO of ventures. He enjoys developing and innovating products, which makes him a unique, versatile developer with excellent knowledge of how to conceive a product from scratch and solve problems in a very efficient way. He can fluently program in Java, Swift, JavaScript, and PHP at the same time.


Java, Openfire, PHP, MySQL, XMPP, NATS, Android, APIs, API Integration, CSS...
UV Partners, Inc.
Java, Swift, Android, iOS, GraphQL, REST, Bluetooth LE, ESP32, Mobile UX...
Popular Pays Inc
Swift, APIs, API Integration




Preferred Environment


The most amazing...

...platform I've built is Klassroom.co, the #1 communication platform between parents and teachers in France with over 50 countries and 1.5 million users.

Work Experience

CTO | Co-founder

2015 - PRESENT
  • Developed the company from zero to 1.5 million active users.
  • Put in place a process to manage the team of developers with Slack, Jira, and GitHub.
  • Oversaw the back end from mobile Swift and Java to web React and the server side in Java.
  • Created a real-time chat application used by millions of people through the web, Android, and iOS.
Technologies: Java, Openfire, PHP, MySQL, XMPP, NATS, Android, APIs, API Integration, CSS, CSS3, CTO, Data Scraping, HTML, HTML5, iOS, Laravel, MacOS, JavaScript, Mobile Web, Node.js, OAuth 2, React, REST, REST APIs, SDKs, Software Architecture, SQL, Stripe, Stripe API, Swift, Symfony, Technical Leadership, XML, Vue, User Experience (UX), User Interface (UI), SwiftUI

Mobile App Developer

2022 - 2022
UV Partners, Inc.
  • Developed features and fixed bugs in Android and iOS.
  • Interacted with IoT devices with BLE and ESP32 API to connect them with iOS and Android devices.
  • Tracked, fixed, and improved the productivity of their product.
Technologies: Java, Swift, Android, iOS, GraphQL, REST, Bluetooth LE, ESP32, Mobile UX, Mobile UI

Senior iOS (Swift) Developer

2022 - 2022
Popular Pays Inc
  • Helped develop new features for a social media application in iOS using Swift.
  • Tracked and fixed bugs in Jira and Trello and used Travis CI.
  • Fixed Travis CI scripts to improve continuous integration.
Technologies: Swift, APIs, API Integration

CTO Consultant

2012 - 2015
Funbars Group
  • Performed the audit and analysis of their current systems and reverse-engineered the current operating system.
  • Redesigned and coded their entire operating system in PHP and MySQL using Symfony 1.4 and 2.0 framework to manage ten restaurants.
  • Designed and developed their event site—iAdventure.com—and all their restaurant sites.
  • Provided advice regarding SEM and SEO for all their sites and restaurants.
Technologies: PHP, MySQL, Java, JavaScript, iOS, Symphony, CTO, Software Architecture, jQuery, jQuery UI

Founder and CTO

2010 - 2015
  • Partnered with over 300 daily deal websites and 1,000 merchants, generating over $800,000 in revenue for the partners in year two.
  • Owned SEM and SEO strategy with 20 million indexed pages on Google and the #1 page for over 10,000 keywords.
  • Handled accounting and budget and sold to the leading deal site in Holland.
  • Designed and coded the platform in PHP and MySQL using Symphony framework for the back end and jQuery for the front end. I also developed powerful XML and HTML scraping tools and an API for our affiliate network.
Technologies: JavaScript, PHP, MySQL, XML, REST


2011 - 2013
  • Built a gaming platform bundling games and advertising components with NSIS, PHP, and MySQL.
  • Built the back end to handle the affiliate network of publishers.
  • Helped in prospecting and signing up over 70 publishers and the affiliate network to promote our product, resulting in around $500,000 in revenue in 2012.
Technologies: PHP, NSIS, Symfony, MySQL

VP Structured Mexican Interest Rates Broker

2008 - 2010
Tullett Prebon
  • Built a set of powerful analytics for fixed income instruments in Excel, VBA, and MySQL using the OO model. This tool allows to model interest rates curves and price swaptions and CFS to arbitrate between the forwards, swap curves, and bonds.
  • Created Bloomberg screens to display live pricing of swaptions and CFS.
  • Worked with the analytical group to explain the techniques on how to price swaptions and CFS.
Technologies: Excel VBA, MySQL, Java

Emerging Market Trader Associate

2005 - 2007
Deutsche Bank
  • Developed numerous models and pricing tools for asset swaps, inflation swaps, and cross-currency swaps using DB analytics (the Deutsche Bank financial library), VBA, and Excel.
  • Automated and optimized the process of entering trades from the front office blotter to the middle office system using Excel, SOAP, and the system API. This system saved time and a lot of money by removing 95% of manual input errors.
  • Designed a system to send auto-confirmation of each trade to all counterparties, saving around 1-2 hours of work within a day.
  • Designed and developed a system that allows both traders in NY and Mexico to see live risk and P&L and input trades without conflicts on a shared book using Excel and Access.
Technologies: Microsoft Access, Excel VBA, Java, MySQL


A real-time messaging, robust distributed platform that allows communication between parents and teachers with over 1.5 million users. It is present in over 50 countries with a leading market in France.

I built the company from scratch as the CTO and co-founder.

Education App

An education app to improve communication between parents, teachers, and schools with over two million users worldwide. I am the CTO and co-founder, and I developed everything from scratch. I now manage a team of seven developers.


Java, Swift, PHP, JavaScript, XML, HTML5, HTML, CSS, CSS3, SQL, Kotlin, Excel VBA, GraphQL


Symfony, OAuth 2, Laravel, SwiftUI


React, Node.js, REST APIs, Stripe, Stripe API, jQuery, jQuery UI, Vue


REST, Mobile Development


iOS, Android, MacOS, Bluetooth LE




XMPP, Openfire, SDKs, Data Scraping, APIs, Mobile Web, Software Architecture, Technical Leadership, CTO, API Integration, Symphony, Mobile UX, Mobile UI, Web Development, User Experience (UX), User Interface (UI), NATS, ESP32


NSIS, Microsoft Access

2004 - 2005

Master's Degree in Mathematics and Computer Science

Columbia University - New York, NY, USA