Eric Belfer, Developer in Port St. Lucie, FL, United States
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Eric Belfer

Verified Expert  in Engineering

React Developer

Port St. Lucie, FL, United States
Toptal Member Since
October 6, 2021

Eric worked for various startup software companies in San Francisco, mainly in the mobile app gaming space. He moved on to freelancing and helped small and medium-size companies develop client and internal-facing software, create MVPs, and build out and lead their tech team. His specialty is Ruby on Rails and React. Eric also has a lot of experience setting up software infrastructure on cloud computing services such as AWS, Heroku, Digital Ocean, and Google.


Ruby on Rails (RoR), React, Datadog, Heroku, PostgreSQL
React, Angular, Ruby on Rails (RoR), Amazon Web Services (AWS), Heroku, Next.js...
Ruby on Rails (RoR), React, Amazon Web Services (AWS), Heroku...




Preferred Environment

Ruby on Rails API, Ruby on Rails (RoR), React, Next.js, PostgreSQL, Amazon Web Services (AWS), Heroku, Node.js

The most amazing...

...thing I have developed was a real-time event processing system for a top 30 US mobile gaming app with the data stored in AWS Redshift for analysis.

Work Experience

Senior Full-stack Developer

2021 - 2022
  • Leveraged Datadog to find significant performance issues with many timeouts occurring across the site. After finding the causes, built out dashboard widgets with notifications for developers to monitor after deploying new code.
  • Designed the infrastructure and led the team to develop the new onboarding process to add new brands to HelloAbound.
  • Moved our image storage system off of Filestack to ActiveStorage.
Technologies: Ruby on Rails (RoR), React, Datadog, Heroku, PostgreSQL

Senior Full-stack Developer

2018 - 2021
  • Created an eCommerce site built on Next.js and deployed through Vercel. I optimized the site to rank high on search engine queries and set up advertising and internal site tracking.
  • Guided the startup,, on setting up their Rails API back end.
  • Tracked and fixed bugs using Trello as a reporting tool for a small startup,
Technologies: React, Angular, Ruby on Rails (RoR), Amazon Web Services (AWS), Heroku, Next.js, Amazon DynamoDB, AWS Lambda

Senior Full-stack Developer

2018 - 2021
  • Led software teams that built out custom software for a range of industries.
  • Created an internal tool for workers to evaluate and track variations of agriculture seed data in the field where internet connection is limit or non-existent. The company, HoladaySeed, is based out of California with employees across North America.
  • Upgraded and built-out features for a large home builder, Classic Homes, internal Rails system to create custom contracts.
  • Developed an MVP monthly subscription journal website to see if users would be willing to pay a premium to receive local political news that affected their community. The app was built leveraging Rails and React.
  • Set up a mobile API with Rails for LittleProfessor's customer-facing app to purchase books and track orders. Also, I developed an admin dashboard with ActiveAdmin to track orders and inventory.
Technologies: Ruby on Rails (RoR), React, Amazon Web Services (AWS), Heroku, Agile Software Development, ActiveAdmin, APIs, Next.js

Senior Full-stack Developer

2019 - 2020
  • Led a team in building out an internal training tool for Modine, a heating and air conditioning company.
  • Set up automatic deployment infrastructure to allow for continuous development. The system had an automated test ran by CircleCI.
  • Tracked timelines of features using Jira to ensure the team would hit our deadlines for estimated completion dates.
Technologies: Next.js, React, Express.js, Amazon Web Services (AWS), MongoDB

Lead Analytics Software Developer

2017 - 2018
  • Developed an in-house product for processing and storing in-game time-series events on AWS Redshift.
  • Created SQL views, dynamic graphs, and daily reporting tools to show the prospective lifetime monetary value of users from in-game activity. These tools provided analysts a way to deep dive into the data and generate custom reports from curated data.
  • Developed a user retargeting program to do A/B testing for in-game notifications and provide metrics on each user segment over time.
Technologies: Ruby on Rails (RoR), Redshift, Amazon Web Services (AWS), Amazon EC2, PostgreSQL

Lead Server Engineer

2016 - 2017
  • Built a dynamic back-end server startup and downturn system to react to in-game activity spikes. I improved overall server costs by 35% and removed the human element.
  • Developed and maintained their user acquisition platform to track spending, installs, revenue, and other metrics on ad campaigns on over 10 advertising platforms.
  • Oversaw launches for new version releases for a top 30 mobile game in the US app store.
Technologies: Ruby on Rails (RoR), Amazon Web Services (AWS), Amazon S3 (AWS S3), Amazon DynamoDB, Amazon EC2, AWS ALB

Back-end Developer

2014 - 2016
  • Reduced in-game tournament battles back-end processing time by two times faster by leveraging memcached to cache all types of monsters across the users who entered the tournament, reducing overall costs of hosting tournaments.
  • Tracked and fixed bugs using Jira as a reporting tool.
  • Built an API replay script to better test complex mobile game interactions without the need to walk through the game and make interactions. Also, I reduced time spent on back-end development testing before the new version launches by around 40%.
Technologies: Amazon Web Services (AWS), Ruby on Rails (RoR), Amazon DynamoDB, Amazon EC2, Memcached

An MVP Rails-based monthly subscription newspaper site that features articles on local political issues. The idea is to see if people would be interested in deep diving into political topics directly related to them and their local community. The site's goal is to test user traction. Therefore, we integrated Optimizely to allow admin users to create various A/B experiments. The app also integrates monthly recurring payments with Recurly, and the payment processing piece integrates with PayPal, Apple Payments, and Stripe. Finally, the app users ActiveAdmin to create a simple framework for admin adjustments and reporting on the administrative side.

A Rails-based app is a literature publishing platform driven by the scripts submitted by the community. Authors post partial or complete manuscripts to the site, readers vote on the scripts submitted, and then the Inkshares publishing team selects the tops scripts to publish in the traditional sense. I was one of the back-end developers on the project. A significant feature I built out was the search functionality for the site, which integrates with Algolia Search. In addition, it allowed for dynamic typeahead searching on all manuscripts. Another feature that I spearheaded was the payment service which leveraged Stripe to process the payments.

Goodbye to Muck & Weeds!
The app is an eCommerce site built with Next.js and an AWS Lambda API back end connected to DynamoDB. Vercel is used to make app deployments. The app is 100% server-side rendered, which leverages Vercel's CDN. The app has a blog that leverages Cosmic JS, a headless CMS, to allow new blog pages to be added monthly by the owner to improve Google site rankings. The app also has multiple URL endpoints for serving customers in Europe vs. Northern America as pricing, shipping, catalog of products, and languages change between the two regions. I was the lead developer and worked with the design team to bring the app from an idea to production. The app is simple but leverages various advanced technologies to create a fast and robust site.

Toptal Node.js Accelerator

The Node.js Accelerator is an exclusive learning program that educates JavaScript and back-end developers in Node.js, ExpressJs, NestJS, and TypeScript. This is a two-month program that consists of rigorous learning exercises, live instructor-led sessions by SMEs, hands-on activities along with a stringent evaluation process, comprehensive assessments, and an incremental project where participants implement a couple of Microservices (REST APIs) using Express.js and Nest.js. The incremental project simulates an eCommerce application consisting of two services, i.e., a user service to implement the authentication with user management and a product-catalog service that offers functionalities to manage inventory.
2010 - 2014

Bachelor's Degree in Computer Science, Industrial and Operations Engineering

University of Michigan - Ann Arbor, MI


Toptal Node.js Accelerator Graduate

Toptal, LLC


Ruby on Rails API, React, Node.js, Stripe, Cosmic JS


Recurly, Optimizely


Ruby on Rails (RoR), Ruby on Rails 4, Next.js, Tailwind CSS, Angular, Express.js, NestJS


Agile Software Development


SQL, JavaScript, TypeScript


Heroku, Amazon Web Services (AWS), AWS Lambda, Amazon EC2, AWS ALB


PostgreSQL, Amazon S3 (AWS S3), Amazon DynamoDB, Redshift, MongoDB, Memcached, Datadog


APIs, LogRocket, ActiveAdmin, Content Delivery Networks (CDN)

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