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Sergio Marquez
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Senior Software / Product Engineer / Rails · JavaScript · React

Hi, I’m Sergio

I’m a code-first Senior Software / Product Engineer who builds and modernizes web products across Ruby on Rails, JavaScript, React, APIs, and full-stack systems.

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01 / About

I’m a code-first Senior Software / Product Engineer. Since 2011, I’ve built and modernized production web products across Ruby on Rails, JavaScript, React, APIs, and full-stack systems.

I stay close to users and carry context from discovery into systems design, product decisions, implementation, and production ownership. Outside work, I’m usually surfing, learning something new, or finding a better way to make things work.

02 / Experience

Career record / 2011—now

A career spent close to users, from early product delivery to technical leadership and product discovery. Selected outcomes stay in the role summaries; the complete record follows.

  1. 01 —NOW REMOTE / CONTRACT

    KaiPod Learning

    Education technology

    Senior Product Engineer (Ruby on Rails)

    CURRENT

    Supports independent microschool founders through training, partner services, and Newton management software.

    Works with founders and teachers to turn operational needs into role-based workflows across Ruby on Rails and Hotwire Native. Ships product features, including a teacher-facing AI task generator and recurring Stripe billing with customizable per-student plans.

    Contribution notes
    • Partners with microschool founders and teachers to turn operational needs into product workflows.
    • Works across product discovery, user research, systems analysis, design, technical planning, and production delivery within a four-developer team.
    • Builds role-based experiences for school owners, staff, teachers, parents, and students across web and Hotwire Native applications.
    • Expanded real-time messaging with announcements, search, reactions, read receipts, and threaded conversations, then improved its performance through query optimization and layered caching.
    • Shipped a teacher-facing task generator using structured output, with controls to select, regenerate, or edit generated tasks before use.
    • Implemented Stripe APIs and webhooks for recurring monthly billing and customizable per-student plans.
    • Ruby on Rails
    • Hotwire Native
    • PostgreSQL
    • Stripe
  2. 02 — REMOTE / LEADERSHIP

    Decisiv, Inc.

    Commercial transportation software

    Lead Software Engineer

    02 / 08

    Provides Service Relationship Management software for commercial-vehicle maintenance and repair.

    Reduced affected page-load times by 20% to 80%, cut CircleCI feedback from approximately 40 minutes to 8 minutes, and led incremental Rails and Ruby modernization.

    Contribution notes
    • Reduced affected page-load times by 20% to 80% through bounded queries, N+1 elimination, lighter JavaScript, and asynchronously loaded React widgets.
    • Cut CircleCI workflow time from approximately 40 minutes to 8 minutes through test-suite modernization, flaky-test reduction, Capybara testing, and parallel execution.
    • Led incremental modernization of more than 500,000 lines from Rails 4.0 and Ruby 1.8 to Rails 7.0 and Ruby 3.1.
    • Ruby on Rails
    • React
    • Datadog
    • CircleCI
  3. 03 — REMOTE / FULL-STACK

    Decisiv, Inc.

    Commercial transportation software

    Ruby on Rails Engineer

    03 / 08

    Provides Service Relationship Management software for commercial-vehicle maintenance and repair.

    Redesigned and redeveloped product applications while improving API performance and interoperability.

    Contribution notes
    • Built features across a server-rendered product platform and its supporting APIs.
    • Integrated third-party applications with the core system to expand functionality.
    • Ruby on Rails
    • Ruby
    • PostgreSQL
    • Redis
  4. 04 — ON-SITE / WELLINGTON

    Paper Kite Ltd

    Digital product agency

    Ruby on Rails Engineer

    04 / 08

    Designs and develops mobile and web products for clients.

    Developed Ruby on Rails APIs for mobile products, external services, and payment integrations.

    Contribution notes
    • Worked across BPme New Zealand, All Blacks, and AMPM Scratch Power.
    • Built data-analysis tools to help clients understand user behavior and needs.
    • Ruby on Rails
    • APIs
    • Payments
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  1. 05 — REMOTE / CONTRACT

    ThinkCERCA

    Education technology

    Ruby on Rails Engineer

    05 / 08

    Provides an online literacy and critical-thinking platform for grades 4-12.

    Designed and developed APIs for a content-loading system and contributed across student, lesson, and educator workflows.

    Contribution notes
    • Built Ruby and Rails APIs used to load production content.
    • Contributed to content access and automated testing.
    • Ruby on Rails
    • Ember.js
    • Capybara
  2. 06 — ON-SITE / MAR DEL PLATA

    DevSpark

    Software services

    Mid Senior Ruby on Rails Engineer

    06 / 08

    Nearshore software development company, later known as Spark Digital.

    Designed, developed, and tested recruitment, insurance-workflow, and internal API applications while coordinating with an overseas team.

    Contribution notes
    • Worked across customer support, third-party endpoints, multiple databases, and PDF/XDF generation.
    • Progressed to managing a customer project after demonstrating rapid learning and adaptability.
    • Ruby on Rails
    • AngularJS
    • PostgreSQL
    • jQuery
  3. 07 — ON-SITE / MAR DEL PLATA

    SoftPro SRL

    Software services

    Junior Full-Stack Software Developer

    07 / 08

    Software development company providing tailored, end-to-end solutions across web, mobile, and desktop platforms.

    Designed and developed web products across design and full-stack implementation, then helped new coworkers learn the stack.

    Contribution notes
    • Designed and developed a casino-management web application and other core products.
    • Trained new coworkers in Ruby on Rails, jQuery, CSS, and Ajax.
    • Ruby on Rails 3.2
    • jQuery
    • Bootstrap
    • Haml
  4. 08 — FREELANCE

    Freelance

    Independent software development

    Freelance Full-Stack Web Developer

    08 / 08

    Commercial-management and field-sales web applications.

    Designed and developed web applications for commercial-management and door-to-door sales workflows.

    Contribution notes
    • Built a commercial-management web application with PHP, jQuery, and Ajax.
    • Developed a mobile website for door-to-door sales workflows.
    • PHP
    • PHP ActiveRecord
    • jQuery Mobile

Selected community project

Hacer Pedido

Volunteer community project · COVID-19 pandemic Distributed team / Argentina · Spain · Germany

A small volunteer community project during COVID-19, helping local businesses publish simple menus and take orders remotely.

What we shipped / A simple ordering path that helped participating local businesses take orders remotely.

Contribution notes

I joined the later rewrite, not the original WordPress version. As part of a small distributed volunteer team, I worked across UX and frontend/full-stack delivery. Businesses could manage menu information, and customers could review a cart before handing the order off to a prefilled WhatsApp message.

03 / Technical focus

A practical stack for durable product work. Prioritized, not exhaustive.

  • 01Ruby / Rails / APIs
  • 02JavaScript / React / Hotwire
  • 03PostgreSQL / Redis / Stripe
  • 04Product discovery / performance / CI/CD

Let’s build something useful.

Reach out about long-term remote product work with stable teams that stay close to users and own products over time.