Joaquín is available for hire
Hire JoaquínJoaquín Freyer
Verified Expert in Engineering
Full-stack RoR and React Developer
Madrid, Spain
Toptal member since October 8, 2025
Bio
Joaquín is a senior software engineer with over five years of experience specializing in back-end development. With a strong command of Ruby on Rails (RoR), Node.js, and React, he builds robust, scalable systems that power real-world products. Joaquín holds a computer science degree from ORT University and thrives in collaborative environments where teamwork turns ideas into impactful solutions.
Portfolio
The Hawk Eye Football
Python, React, FastAPI, Redux, Plotly.js
Authorium
Ruby on Rails 8, Hotwire, Turbo, Stimulus, CKEditor, Formio, Claude Code...
String and Key
Ruby on Rails 8, API Integration, Web Development, Ruby, Ruby on Rails (RoR)...
Experience
- Agile Software Development - 6 years
- Scrum Master - 6 years
- APIs - 6 years
- Ruby on Rails 8 - 6 years
- Ruby - 6 years
- Software Architecture - 3 years
- Node.js - 3 years
- Cursor AI - 1 year
Preferred Environment
MacOS, Cursor AI, Ruby on Rails (RoR), React, Node.js
The most amazing...
...app I've developed is a movie recommendation app with an AI boost that learns users' tastes, blends content and behavior, and serves spot-on picks in real time.
Work Experience
Co-founder & CTO
2025 - PRESENT
The Hawk Eye Football
- Architected and built a football analytics platform from scratch using Python/FastAPI and PostgreSQL, integrating Wyscout as the primary data source for team, match, and event-level statistics.
- Engineered a derived analytics layer with precomputed advanced stats tables (team_season_advanced_stats) using complex JSONB aggregation logic in PostgreSQL, reducing query latency for downstream consumers.
- Built a Team Analytics module that transforms raw event data into actionable performance metrics for scouting and tactical analysis.
- Founded and led the end-to-end development of Hawkeye Football, a football analytics and scouting platform targeting professional clubs and analysts.
- Established a planning-first engineering workflow leveraging AI tooling (Claude Code) to autonomously explore the codebase and produce structured execution plans before implementation, accelerating delivery on a solo-founder timeline.
- Designed and implemented data pipelines ingesting team statistics, match-level metrics, and granular match events from Wyscout into a normalized PostgreSQL schema.
- Launched the public landing page and product positioning at thehawkeyefootball.com, owning brand, domain configuration, and deployment infrastructure.
- Integrated AI-assisted engineering workflows (Claude Code with custom hooks and session tooling) to plan and execute back-end features autonomously, reducing time-to-prototype on complex data modeling tasks.
Technologies: Python, React, FastAPI, Redux, Plotly.js
Full-stack Software Engineer
2025 - PRESENT
Authorium
- Led development of a multi-step approval routing engine in a Rails monolith for government procurement. Extended approver types, fixed state machine bugs, and patched a security vulnerability in a zero-downtime production environment.
- Built a full CKEditor 5 rich text toolbar for approval workflows, including variable preview (MergeFields), media, tables, and typography. Solved layout challenges with scoped CSS and fixed editor lifecycle bugs with Turbo/Stimulus.
- Refactored approval activity logs for auditability: consolidated granular entries into structured per-document logs, extracted shared components, and replaced timestamp-based change detection with version tracking to eliminate false positives.
Technologies: Ruby on Rails 8, Hotwire, Turbo, Stimulus, CKEditor, Formio, Claude Code, Full-stack Development, Architecture, Full-stack
Senior Back-end Engineer
2023 - 2024
String and Key
- Developed and automated the insurance policy reinstatement process, improving accuracy and reducing manual intervention.
- Created a referral system to boost user acquisition and engagement.
- Integrated SmartyStreets to automate address verification, improving data accuracy and reducing failed deliveries.
Technologies: Ruby on Rails 8, API Integration, Web Development, Ruby, Ruby on Rails (RoR), SQL, PostgreSQL, Payments, Stripe, GraphQL, Architecture
Back-end Technology Lead
2022 - 2023
The Humane Space
- Built a versioned REST API structured with the MVC pattern, improving code organization, extensibility, and long-term maintainability.
- Integrated Mailchimp to automate marketing campaigns and improve customer engagement through targeted communications.
- Implemented a unified subscription manager for Apple and Android platforms, automating monthly and yearly plan handling to improve revenue tracking and user retention.
Technologies: Ruby on Rails 8, Mailchimp, REST APIs, API Integration, Web Development, Ruby, Ruby on Rails (RoR), REST, SQL, PostgreSQL, Payments, Architecture, Technical Leadership
Senior Back-end Engineer
2022 - 2022
Doctor Daugthers
- Built a medical history management system with the Administrate gem, enabling efficient data handling and improving administration usability.
- Secured application data through comprehensive encryption, strengthening privacy and compliance with security standards.
- Handled Aptible deployments, optimizing performance, uptime, and compliance for hosted applications.
Technologies: Ruby on Rails 8, Aptible, Web Development, Ruby, Ruby on Rails (RoR), REST, PostgreSQL, Architecture, Technical Leadership
Senior Lead Engineer
2021 - 2022
Rate & See
- Created an AI-powered web application that recommends movies by analyzing similarities between users' viewing preferences, delivering personalized and accurate suggestions.
- Reached over 95% RSpec test coverage, ensuring code reliability and reducing regressions during feature releases.
- Oversaw deployment operations, ensuring smooth releases, minimal downtime, and consistent environment stability.
- Led the development of the full UI using React, building a modular and responsive interface that improved user experience and front-end scalability.
Technologies: Ruby on Rails 8, Artificial Intelligence (AI), RSpec, API Integration, Web Development, Ruby, Ruby on Rails (RoR), REST, PostgreSQL, React, Redux, Next.js, Full-stack Development, TypeScript, Architecture, Full-stack, Technical Leadership
Experience
The Hawk Eye Football
http://thehawkeyefootball.comThe Hawk Eye Football is a football analytics platform built for clubs, coaching staffs, scouts, and sporting directors.
We come from two paths that rarely meet in football in this part of the world.
On one side, a decade of international scouting, advisory work with professional clubs, and direct experience as a player in Europe and South America.
On the other hand, specialized training in data science applied to football, along with years of professional work in data analysis and software development.
What we're building is a platform that combines team analysis, player scouting, match preparation, and squad building, with one clear premise: every analysis and every visualization has to answer a concrete football question.
We work with Wyscout/Hudl data and build our own analytical layers on top of it.
We're starting in Uruguay, with our sights set on the rest of the region. We're still in build mode, and over the coming months, we'll be sharing pieces of what we're working on.
We come from two paths that rarely meet in football in this part of the world.
On one side, a decade of international scouting, advisory work with professional clubs, and direct experience as a player in Europe and South America.
On the other hand, specialized training in data science applied to football, along with years of professional work in data analysis and software development.
What we're building is a platform that combines team analysis, player scouting, match preparation, and squad building, with one clear premise: every analysis and every visualization has to answer a concrete football question.
We work with Wyscout/Hudl data and build our own analytical layers on top of it.
We're starting in Uruguay, with our sights set on the rest of the region. We're still in build mode, and over the coming months, we'll be sharing pieces of what we're working on.
Presale Platform Optimization
https://presale.effectussoftware.com/This project involved building an AI-powered agent integrated into the presale platform to automatically analyze, categorize, and prioritize incoming leads based on predefined criteria such as engagement level and industry. This significantly improved the sales team's efficiency, response time, and overall lead management accuracy.
Education
2018 - 2024
Bachelor's Degree in Computer Science
ORT University - Montevideo, Uruguay
Certifications
JUNE 2023 - PRESENT
Certified Scrum Master
Peregrinus
Skills
Libraries/APIs
React, Node.js, Stripe, REST APIs, Plotly.js
Tools
Claude Code, Mailchimp, RSpec, Hotwire, Turbo, CKEditor, n8n
Languages
Ruby, SQL, GraphQL, JavaScript, CSS, HTML, TypeScript, Python
Frameworks
Ruby on Rails (RoR), Next.js, Redux, Stimulus
Paradigms
Agile Software Development, REST
Platforms
MacOS, Apache Kafka, Software Design Patterns, Vercel, Aptible, Amazon Web Services (AWS)
Storage
PostgreSQL
Other
APIs, Scrum Master, Ruby on Rails 8, API Integration, Web Development, Architecture, Full-stack, Technical Leadership, Software Architecture, Cursor AI, Artificial Intelligence (AI), AI Tools, Full-stack Development, Payments, Algorithms, Open-source LLMs, Computer Science, Large Language Models (LLMs), FastAPI, Vite, Formio
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