Federico Dayan, Developer in El Bolsón, Río Negro, Argentina
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Federico Dayan

Bio

Federico is a staff/principal-level software engineer with 20+ years of experience designing, building, and scaling web applications and distributed systems. He has a strong track record of creating startup MVPs and taking products from 0 to 1 through production-ready platforms. With deep expertise in system design, API architecture, and full-stack development, Federico is comfortable leading architectural decisions, mentoring engineers, and remaining hands-on with complex, high-impact systems.

Portfolio

Fellows Butler Ventures Inc.
TypeScript, Data Modeling, System Design, Application Architecture, PostgreSQL...
Instrumentl
Ruby on Rails 4, Stimulus, Redis, PostgreSQL, API Development...
Class Twist Inc. dba ClassDojo
TypeScript, React, Next.js, Gatsby, JavaScript, Node.js, GraphQL, Twilio...

Experience

  • SQL - 12 years
  • Ruby - 9 years
  • Scrum - 9 years
  • Ruby on Rails (RoR) - 9 years
  • React - 8 years
  • TypeScript - 3 years
  • Cypress - 3 years
  • Next.js - 2 years

Preferred Environment

Terminal, MacOS, ChatGPT, Claude Code

The most amazing...

...: I build end-to-end full-stack products from scratch, from APIs to UI, modernize legacy systems, and ship scalable, well-tested apps that solve real problems.

Work Experience

Node.js/React Developer

2026 - PRESENT
Fellows Butler Ventures Inc.
  • Built Orbit from 0 to 1 as the first engineer: an AI-assisted SaaS platform helping teachers manage high-pressure crises involving neurodivergent children.
  • Designed a cloud-native architecture using Next.js, TypeScript, PostgreSQL, Docker, Google Cloud, and Pulumi-managed infrastructure.
  • Used Claude Code and AI workflows heavily, including agents, skills, planning docs, implementation plans, refactoring, and review loops.
Technologies: TypeScript, Data Modeling, System Design, Application Architecture, PostgreSQL, REST APIs, API Development, Cloud Architecture, React, Node.js, Security, Audits, VPS, Code Review, Claude, Workflow Automation, Communication, AI Agents, Artificial Intelligence (AI), HTML5

Senior Full-stack engineer

2025 - 2026
Instrumentl
  • Worked on a pod of five developers to add, improve, and fix features in the grant's tracker. Involved mainly in the expenses and financials part.
  • Worked as a full-stack developer in UI components as well as back-end and API endpoints.
  • Tried and tested different AI SDKs to integrate into different features of the app for a better user experience.
Technologies: Ruby on Rails 4, Stimulus, Redis, PostgreSQL, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development, AI Tools, Session Handling, Google Cloud Platform (GCP), Claude Code, Claude Agent SDK, Cursor AI, SQLite, Code Review, Claude, Workflow Automation, Communication, AI Agents, Artificial Intelligence (AI), HTML5

Web Engineer

2024 - 2025
Class Twist Inc. dba ClassDojo
  • Refactored a Gatsby app to improve building and web performance. Reduce building time by 90% for faster iterations.
  • Worked closely with designers to implement a design system and a React UI kit.
  • Migrated Gatsby to Next.js to handle being able to profit from back-end features.
Technologies: TypeScript, React, Next.js, Gatsby, JavaScript, Node.js, GraphQL, Twilio, React Testing Library, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Vite, Vitest, Cloudflare, Back-end Development, Session Handling, SQLite, Code Review, Claude, Communication, AI Agents, Artificial Intelligence (AI), HTML5

Lead Engineer

2023 - 2024
Pearl Edison
  • Architected and developed an onboarding app from scratch to capture users' requirements for the new cooling or heating equipment for their homes.
  • Crafted and built the process of configuring orders and tracking installations and payments.
  • Designed and developed the admin side to configure and track orders.
Technologies: React, TypeScript, Next.js, Node.js, tRPC, API Design, Supabase, Technical Leadership, Cloud Architecture, Minimum Viable Product (MVP), Stripe, React Testing Library, Payment APIs, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development, Session Handling, AWS IoT, NGINX, Code Review, Communication, Google AppSheet, HTML5

Full-stack React and RoR Developer

2023 - 2023
Fieldcraft, Inc.
  • Converted UI/UX mockups to React screens and components.
  • Developed REST API endpoints in Ruby on Rails end to end.
  • Implemented best practices in Next.js, React, Tailwind CSS, and Ruby on Rails.
Technologies: React, Next.js, Ruby on Rails (RoR), PostgreSQL, APIs, Tailwind CSS, CSS, FedEx API, SendGrid API, Stripe API, API Integration, Node.js, Front-end Design, Web Development, Full-stack, Gatsby, Front-end, Technical Consulting, Technical Architecture, Material UI, React Router, Axios, GitHub, SDKs, User Interface (UI), User Experience (UX), Full-stack Development, Deployment, Architecture, Cloud, Automation, Test-driven Development (TDD), Figma, API Design, React Testing Library, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development, Session Handling, AWS IoT, NGINX, Code Review, Communication

Senior Software Engineer

2021 - 2023
TaskRabbit
  • Developed React components and Next.js page for the TaskRabbit marketplace.
  • Wrote Jest tests for components and E2E test in Playwright.
  • Created Ruby on Rails REST endpoints to be consumed by React.
Technologies: Ruby on Rails (RoR), Ruby, TypeScript, Next.js, React, Storybook, Playwright, Web, MySQL, Docker, APIs, Webhooks, CI/CD Pipelines, Node.js, GraphQL, Microservices, Babel, API Integration, React Native, Vercel, Storyblok, Front-end Design, Web Development, Full-stack, Front-end, Nx, Monorepos, Technical Consulting, Technical Architecture, Material UI, React Router, Axios, GitHub, eCommerce APIs, Integration, SDKs, User Interface (UI), User Experience (UX), Full-stack Development, Deployment, Architecture, Cloud, Automation, Test-driven Development (TDD), Figma, SEO Tools, API Design, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development, Session Handling, AWS IoT, Code Review, Communication

Senior Full-stack Developer

2021 - 2021
WeSpire
  • Created UI components in React for managing different components such as volunteering, donation, campaigns, and idea boards.
  • Developed GraphQL queries to be consumed by React components.
  • Constructed controllers, views, and models in Ruby on Rails for the admin to manage the platform.
Technologies: Ruby, Ruby on Rails (RoR), React, RSpec, Cypress, Web, Single Sign-on (SSO), Tailwind CSS, APIs, CI/CD Pipelines, GraphQL, Babel, API Integration, Node.js, Web Development, Full-stack, Front-end, Technical Consulting, Technical Architecture, Material UI, React Router, Axios, GitHub, Integration, SDKs, User Interface (UI), User Experience (UX), Full-stack Development, Deployment, Architecture, Cloud, Automation, Test-driven Development (TDD), Figma, Go, SEO Tools, Ruby on Rails 4, API Design, AWS Lambda, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development, Code Review

Senior Full-stack Developer

2020 - 2020
TrackerBuddy
  • Developed an application to keep track of different metrics of mental health and habit tracking. The user was able to go to the app daily and keep track of his moods, anxiety, sleep, sadness, and more.
  • Developed the ability to create custom trackers and built components in React and Ruby on Rails.
  • Built a user interface to display the tracker's data in different ways: calendars, line charts, and bar charts.
  • Used Redux for state management, developed action creators and reducers.
  • Led the team with agile and scrum best practices like stand-ups, user stories, iteration planning, and retrospectives.
  • Built the entire control flow, from sign-up to login and account deletion. Developed React components and Ruby on Rails models and controllers.
  • Developed a responsive application to work on mobile devices.
  • Created jobs in Sidekiq for sending recurrent emails and DB data processing.
  • Developed an API for front-end React components with token authentication.
Technologies: RSpec, Sidekiq, Responsive Design, Redux Thunk, SQL, Firebase, Heroku, PostgreSQL, JavaScript 6, Redux, React, Ruby on Rails (RoR), Ruby, Web, Create React App, APIs, Webhooks, CI/CD Pipelines, GraphQL, Express.js, Babel, API Integration, Wix, Node.js, React Native, Web Development, Full-stack, Front-end, Technical Consulting, Technical Architecture, Axios, GitHub, SDKs, Cloud Firestore, User Experience (UX), Full-stack Development, Deployment, Architecture, Cloud, Automation, Test-driven Development (TDD), Ruby on Rails 4, RabbitMQ, API Development, Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development, Firebase Authentication

Senior Full-stack Developer

2020 - 2020
Awesome Doc
  • Developed a community-based application for rating and recommending doctors. Users were able to ask for recommendations to friends, creating a list of selected practitioners.
  • Developed React components and tested them using Jest.
  • Built controllers and models in Ruby on Rails and tested them using RSpec.
  • Used agile best practices for organizing tasks and responsibilities.
  • Developed a responsive application to work on mobile devices.
Technologies: Responsive Design, SQL, JavaScript, ECMAScript (ES6), MobX, Antd, Jest, React, Ruby on Rails (RoR), Web, Create React App, APIs, Node.js, Web Development, Full-stack, Front-end, Technical Consulting, Technical Architecture, GitHub, SDKs, Full-stack Development, Deployment, Architecture, Cloud, Automation, Test-driven Development (TDD), Application Architecture, System Design, Data Modeling, Security, CSRF Protection, Back-end Development

Senior Full-stack Developer

2019 - 2019
Children's Council San Francisco
  • Led the development of a search engine for connecting eligible families to a subsidized childcare service.
  • Integrated the search engine app with a WordPress application.
  • Developed components and controllers in Angular as part of the architecture of the application.
  • Interacted with designers to integrate images, UI, and UX.
  • Developed a unit test in RSpect and a feature test in Cucumber.
Technologies: REST APIs, SQL, JavaScript, CoffeeScript, Ruby on Rails (RoR), Web, MySQL, CI/CD Pipelines, Node.js, Web Development, Technical Consulting, GitHub, SDKs, Full-stack Development, Deployment, Architecture, Test-driven Development (TDD), SEO Tools, Application Architecture, System Design, Data Modeling, Security, Google Sheets, CSRF Protection, Back-end Development

CTO

2018 - 2019
HipChip
  • Developed a web application for making group gifts—it enables users to send money to a pool and the administrator to buy a gift card for a recipient with that money.
  • Migrated a web application to a new solution utilizing a higher design quality and best practices in Ruby on Rails and JavaScript; implemented an agile process for development, continuous integration, and unit testing.
  • Integrated 3rd-party APIs for getting gift cards and processing payments.
Technologies: REST APIs, RSpec, JavaScript, Ruby on Rails (RoR), Web, CI/CD Pipelines, GitHub, eCommerce APIs, Integration, SDKs, Full-stack Development, Architecture, Test-driven Development (TDD), Python, SEO Tools, Cloud Architecture, System Design, Data Modeling, Audits, Back-end Development

Senior Full-stack Developer

2018 - 2019
California Court Digital Service
  • Led the development of a plugin for searching courts in React that allowed displaying them in a very friendly way to the user. The purpose of the app was to improve the experience of the search result.
  • Connected the front end of the app with the Google Spreadsheets API for the search.
  • Interacted with designers to integrate design with UI, images, and UX.
  • Wrote tests in Jest for testing the React components.
  • Wrote tests using Puppeteer for end-to-end testing of use cases.
Technologies: SQL, JavaScript, MobX, Jest, ECMAScript (ES6), React, Web, Web Scraping, Full-stack Development, Architecture, Test-driven Development (TDD), Data Modeling, Back-end Development

Senior Rails Developer

2017 - 2018
Corsis
  • Developed a web application that enabled clients to browse their IT ratings and allowed over-time comparison of ratings with other performers in the IT industry.
  • Developed an admin application for handling users, profiles, clients, and access to the main application.
  • Developed a web application with AngularJS for letting SMEs collect company data in a practical way.
  • Wrote feature tests with Cucumber for testing functionality.
  • Refactored legacy code to incorporate a new design.
Technologies: JavaScript, Ruby on Rails (RoR), Ruby, Web, SDKs, Architecture, Test-driven Development (TDD), Cloud Architecture, Audits

Senior React/Rails Developer

2017 - 2018
Housing.sfgov.org
  • Developed a web application for handling applications for housing in San Francisco.
  • Created the back-end API in Rails connected to Salesforce.
  • Wrote tests in Jest, RSpec, and puppeteer for testing components.
  • Created reusable components in React to be integrated in the app.
  • Interacted with Salesforce using custom Salesforce SOQL language.
Technologies: Salesforce, React, Ruby on Rails (RoR), Ruby, Web, Architecture, Test-driven Development (TDD), Audits

Full-stack Developer

2015 - 2016
Instrumentl
  • Implemented Agile best practices for organizing the team.
  • Refactored a legacy Rails app to handle more load and use best practices.
  • Covered the web app with unit tests for easier refactoring and implementing of CI.
  • Built a matching framework for finding grants for students.
  • Built a scraper for importing grants from the web.
Technologies: Heroku, Ruby on Rails (RoR), Ruby, Web

Lead Developer

2015 - 2015
iRIPARO
  • Developed a cloud-based web application that was used by more than 86 stores in Europe to process requests for smartphone repairs and returns.
  • Trained and mentored two junior developers to develop stable, supportable Ruby on Rails applications, using recognized standards and best practices.
  • Ensured that all developed applications operated according to customers’ requirements.
Technologies: Bootstrap, Heroku, JavaScript, Ruby on Rails (RoR), Web

Senior Ruby Developer

2014 - 2015
Vydia
  • Developed a web application for helping musicians distribute their content and monetize their videos.
  • Helped current developers using best practices and libraries and mentoring in Agile methodologies (Scrum, CI, TDD, etc).
  • Introduced a continuous integration pipeline: deployment with Capistrano, automatic deployment with Git hooks, regression testing, and all put together with Codeship.
  • Developed a Socket.IO server for collecting video metrics.
  • Maintained, improved, and supported Amazon web service infrastructure: S3, EC2, ELB.
Technologies: Amazon Web Services (AWS), Git, Capistrano, Codeship, Cuba, Ruby, Web

Senior Ruby on Rails Developer

2013 - 2014
MitreMedia
  • Developed a Rails engine for creating WordPress-like applications.
  • Developed Rails engines for administrating websites.
  • Wrote tests using Cucumber, Rspec, and FactoryGirl.
Technologies: REST APIs, Capistrano, Chef, Haml, Sass, jQuery, JavaScript, Ruby, Ruby on Rails (RoR), Web

Lead Ruby on Rails Developer

2011 - 2013
PR Newswire
  • Led the development of a web application that generates HTML content for online advertisement.
  • Developed unit and functional tests.
  • Set up a continuous integration server.
  • Prepared twelve hours' worth of training for the Ruby language and Rails framework.
  • Made a web application responsive for all devices and screen sizes.
Technologies: JavaScript, CoffeeScript, Ruby, Web

Lead Architect

2010 - 2011
Brilig.com
  • Led the architecture of a web application to exchange user data between companies.
  • Developed a web application for collecting and sending user data with a demand of 500 requests per second and a return time of 100ms. The application is running in a cluster of twenty nodes on Amazon EC2.
  • Developed a web application in Ruby on Rails for browsing and purchasing user data.
  • Developed mapreduce applications to manipulate more than 1TB of data in Java and Python.
  • Developed a Ruby on Rails application for managing the database, run reports, transaction, and map reduce jobs.
  • Maintained a distributed index updated in more than five nodes.
  • Implemented a Scrum environment.
Technologies: Java, Ruby, Web, MongoDB, Hadoop

Senior Software Developer

2008 - 2009
Media Math
  • Developed a web application for purchasing online advertisement space automatically.
  • Developed a Ruby on Rails application for managing assets and for an online campaign.
  • Developed Ruby scripts to automate tasks.
  • Developed a scheduler in Java to publish campaigns to three different ad exchanges.
  • Developed the back-end in Java to administer domain model.
Technologies: Web

Senior Software Developer

2007 - 2008
Jones Apparel Group
  • Developed an eCommerce engine.
  • Maintained eCommerce sites for Nine West, Bandolino, Barneys, and Espirit brands.
  • Integrated retail stores with online site inventories.
  • Developed a Ruby on Rails application for running reports.
  • Developed Ruby scripts for manipulating files.
  • Developed reports in SQL.
Technologies: Java, Web

Java Developer

2007 - 2007
Royal Caribbean
  • Contributed to a team of thirty developers responsible for developing points of sale for travel agencies.
  • Consumed web services.
  • Wrote unit tests.
  • Created JSP pages.
  • Maintained JDocs to keep them up to date.
Technologies: Java

Java Developer

2006 - 2007
Tracfone
  • Coded a web application using Spring MVC.
  • Coded models to talk to a rational DB using Hibernate.
  • Developed web services for providing an API.
  • Wrote Unit and Integration tests for models, services, and controllers.
  • Wrote SQL scripts for reporting.
Technologies: Java

Application Developer

2004 - 2006
GlobeTel Communication
  • Developed web services for transferring money from a bank account to a prepaid calling card with Java and Spring. The application was integrated with banks in Mexico and Venezuela through web services. The web service had to support a high demand and was not allowed to be down.
  • Developed a web application for managing the web services, transactions, and clients.
  • Developed various SQL reports.
  • Developed an application for managing the stock options for employees.
  • Managed and added accounts to an Asterix in test environment.
Technologies: Java

ColdFusion Developer

2004 - 2004
Cesuras.com
  • Developed an online pharmacy with ColdFusion.
  • Developed an admin app for managing inventory.
  • Integrated the application with Fedex.
  • Gathered requirements from the client.
Technologies: JavaScript, CSS, HTML

Java Developer

2003 - 2004
Maclee Express
  • Built a web application for taking printing orders in stores.
  • Developed an algorithm for ordering jobs in the most efficient way.
  • Created a web application to work on a touchscreen kiosk.
  • Coded SQL reports for financial use.
  • Developed unit tests with JUnit.
Technologies: Java, Vanilla JS

Java Developer

2002 - 2003
HCPersonal
  • Developed modules for a web application for collecting patient histories.
  • Developed reusable tag libs for the UI.
  • Managed deployments to test and UAT environments.
  • Developed a web service for third-party APIs.
Technologies: HTML, JavaScript, Java, Vanilla JS

PHP Developer

2001 - 2002
Mendquest
  • Developed forums for a client in PHP.
  • Developed and maintained shopping carts in PHP.
  • Supported client content management capabilities for websites.
  • Developed UI using JavaScript and HTML.
  • Set up LAMP environments for deploying PHP web applications.
Technologies: HTML, JavaScript

ASP Developer

1999 - 2000
Científica Sur
  • Developed an online bookstore with ASP.
  • Set up an IIS server for deploying the application.
  • Gathered requirements from clients.
  • Developed database schema for a bookstore.
  • Developed an admin application for managing the bookstore.
Technologies: Active Server Pages (ASP)

Experience

RRList

https://github.com/fddayan/rrlist
Maintains a changing list at a constant size over time.

Erlan MapReduce

https://github.com/fddayan/erlmr
An implementation of distributed MapReduce in Erlang.

Zippo

https://github.com/fddayan/Zippo
A rake DSL for managing Hadoop MapReduce workflows.

Clojure MapReduce

https://github.com/fddayan/pmap_reduce
MapReduce pattern implemented in Clojure.

Teatro y Musica

Website for browsing theaters in Buenos Aires.

Skills

Libraries/APIs

REST APIs, React, jQuery, Node.js, React Router, React Testing Library, API Development, MobX, Facebook API, Antd, Sidekiq, Puppeteer, Playwright, FedEx API, SendGrid API, Stripe API, Stripe, Salesforce API

Tools

Git, Terminal, GitHub, Vitest, Claude, Mercurial, Create React App, Prisma, Nx, Shadcn, RabbitMQ, Google Sheets, Firebase Authentication, Claude Code, NGINX, Chef, Capistrano, Sublime Text, Atom, Babel, Codeship, Redux Thunk, RSpec, Wix, ChatGPT, Figma, Claude Agent SDK

Languages

HTML, CSS, SQL, Sass, JavaScript, Ruby, TypeScript, GraphQL, ECMAScript (ES6), CoffeeScript, HTML5, Java, Active Server Pages (ASP), Haml, JavaScript 6, Go, Python

Frameworks

Redux, Ruby on Rails (RoR), Cypress, Next.js, Tailwind CSS, Express.js, Material UI, Ruby on Rails 4, Vanilla JS, ZURB Foundation 2, Jest, Bootstrap, Hadoop, tRPC, React Native, Cuba, Django, Stimulus, SST

Paradigms

Test-driven Development (TDD), Object-oriented Programming (OOP), Continuous Integration (CI), Model View Controller (MVC), Automation, Application Architecture, CSRF Protection, Agile Software Development, Functional Programming, Extreme Programming, Scrum, Responsive Web Design (RWD), Microservices, Model Context Protocol (MCP)

Platforms

Heroku, Web, Storyblok, Firebase, Ubuntu, MacOS, Linux, Oracle, Amazon Web Services (AWS), Docker, Vercel, AWS IoT, Salesforce, AWS Lambda, Twilio, Google Cloud Platform (GCP), Google AppSheet

Storage

PostgreSQL, SQLite, JSON, MySQL, MongoDB, Membase, HBase, Sybase, Cloud Firestore, Redis

Other

APIs, CI/CD Pipelines, API Integration, Web Scraping, Front-end Design, Web Development, Full-stack, Front-end, Monorepos, Technical Consulting, Technical Architecture, Axios, eCommerce APIs, Integration, SDKs, Full-stack Development, Deployment, Architecture, API Design, Supabase, Technical Leadership, Minimum Viable Product (MVP), System Design, Data Modeling, Vite, Back-end Development, Session Handling, Code Review, Workflow Automation, Communication, AI Agents, Artificial Intelligence (AI), Webhooks, Gatsby, User Interface (UI), User Experience (UX), Cloud, SEO Tools, Cloud Architecture, AI Integration, Payment APIs, Security, Audits, AI Tools, VPS, Responsive Design, Stripe Payments, BrainTree, Storybook, Single Sign-on (SSO), Cloudflare, Cursor AI

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