Guillermo Rentería

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Résumé · Software Engineer

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  • Full StackFrontend and backend, APIs, databases.
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  • BackendPython, Node.js, PHP, data and testing.
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  • Frontend / WebHTML, CSS, TypeScript, Astro, Liquid, accessibility and performance.
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  • QA / Software TesterPlaywright e2e tests, regression, API validation and CI.
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  • Automation & IntegrationsREST and GraphQL APIs, automation and AI agents.
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Guillermo Rentería Hernández

Software Developer

Torreón, Coahuila, Mexico · renteg18@gmail.com · renteriah.github.io · github.com/RenteriaH ·linkedin.com/in/guillermo-renteria-9263052a6

Summary

Software developer and Computer Systems Engineering student with experience on a production Shopify Plus store: web interfaces, REST and GraphQL API integration and data modeling. I work with automated tests and use AI agents while reviewing and verifying every change.

Technical Skills

  • Languages: JavaScript, TypeScript, Python, PHP, SQL, HTML, CSS, Liquid
  • Backend & APIs: REST, GraphQL, Node.js, FastAPI, WebSockets
  • Testing: Playwright, pytest, Vitest, mypy, Core Web Vitals
  • Tools: Git, GitHub Actions, Linux, systemd, Docker, Shopify, Claude Code, Codex

Experience

Software Developer Intern (Professional Residency) — MAHA Home de México

Jul 2026 – Present

Torreón, Mexico · On-site

  • Build responsive components and features for product and cart pages on a production Shopify Plus store using Liquid, HTML, CSS and JavaScript.
  • Integrate and consume Shopify REST and GraphQL APIs, including bulk operations.
  • Organize and model product data with metafields and metaobjects.
  • Automate visual tests with Node.js and Playwright, improve Core Web Vitals and document each change.

Projects

GYMWARRIOR — Academic web store (2024), hardened in 2026

case study

PHP, MySQL, JavaScript, Bootstrap, Playwright

  • Fixed ten security issues with AI assistance: SQL injection (prepared statements), CSRF, unvalidated uploads and non-transactional checkout.
  • Validated the fix with 13 Playwright end-to-end tests: 10 fail on the original and all 13 pass after hardening.

QCE — Real-time market data engine · private repository

Python, FastAPI, WebSockets, DuckDB, Parquet, React, pytest, mypy

  • Defined the architecture and risk rules of a system that ingests REST and WebSocket data, stores it in Parquet and DuckDB, and requires human approval.
  • Directed and reviewed code written mostly by AI agents; about 4,000 Python and 82 React tests, plus mypy and ruff.

Professional portfolio — Bilingual site with CI · public code

GitHub

Astro, TypeScript, Vitest, Playwright, GitHub Actions

  • Shipped a bilingual site, built with AI agents, with content and end-to-end tests and continuous deployment to GitHub Pages.
  • Verified Lighthouse 99–100 performance and 100 accessibility and SEO; a test blocks confidential terms.

Education

B.Eng. in Computer Systems Engineering — Instituto Tecnológico de La Laguna

2022 – Dec 2026 (expected)

Technical High School Diploma in Electronics — CECyTEC

2021

Languages: Spanish (native) · English (basic)