I don't collect technologies — I solve problems and ship the fix to production. Everything below is real and running in production. Where a repository is private it is commercial code, and the live product or a written case study is linked in its place.

🟢 Open to: backend / full-stack roles · full-time · remote or Cali, Colombia 📍 Based in: Cali, Colombia (UTC-5) · 🌐 Remote-first · ⚡ Reply in under 24h

💳 "A payment can never be lost, even if the server dies mid-checkout." Built a checkout Saga orchestrator with the Outbox pattern over Stripe Connect and Wompi: every step is recoverable, every event is delivered. No lost orders, no double charges. → case study

🧾 "Selling online in Colombia requires legal e-invoicing." Integrated DIAN electronic invoicing through the Factus API — invoices generated and reported automatically on every sale. A legal requirement most portfolio projects ignore, solved end-to-end.

🐢 "The product listing took too long under real data." Profiled the ORM, added composite indexes and query projections: 90% fewer database hits on complex lookups. Verified with performance tests, not vibes.

🛡️ "How do you trust a codebase?" You test it like an attacker: 20,927 automated tests at 91.34% line coverage, over a 90% floor the pipeline enforces, plus a nightly CATS suite that throws 150,108 fuzz cases at the API. The fuzzer is not decoration — the latest run is red on 633 findings, 80 of them 5xx responses to malformed input, and they are being worked. Quality is not a promise here — it is a number, including when the number is inconvenient.

🔌 "Frontend and backend always drift apart." Killed the drift: the React storefront consumes a typed SDK auto-generated from the OpenAPI spec — if the API changes, the build breaks before the user notices. A pre-push gate (lint → typecheck → tests → build → bundle budget → e2e smoke) mirrors CI locally: red gate, no push. → shop.cristianarellano.com

📦 "Inventory lived in spreadsheets and memory." (Tigo Colombia) Built Python apps and ETL pipelines from CRM and POS platforms to digitalize inventory control; the rotation reports they produced drove real logistics decisions.

🖥️ "One person keeping a whole site running." (CDA La Luna) Automated monitoring, alerts and backup validation with Python + Bash, hardened servers and managed access control — operational continuity without a night shift.

🤖 "ATS scores are a black box." Built the opposite: a deterministic, explainable CV-scoring engine — six weighted sections, a whole-string match first and a curated alias lexicon only when that misses, and no language model anywhere in the score. Every suggestion re-runs the formula with one gap closed and reports the measured delta. 1,418 test methods across four per-layer test projects, 0 skipped, 0 TODOs in 334 source files. → buildcv-v2 · live

Python  ·  Django  ·  DRF  ·  FastAPI  ·  Celery  ·  GraphQL
PostgreSQL  ·  Redis  ·  SQLite
TypeScript  ·  React 19  ·  Next.js  ·  Node.js (NestJS · Express)
C#  ·  .NET 10  ·  ASP.NET Core
Docker  ·  Linux  ·  GitHub Actions CI/CD  ·  AWS S3/CloudFront
DDD  ·  Hexagonal  ·  Clean Architecture
pytest  ·  Playwright  ·  mypy (strict)  ·  SonarQube  ·  Sentry

The Shoppipai ecosystem — one product, three codebases, built end-to-end. It is a commercial product, so the repositories are private; each row links to the thing you can actually open.

More:

• Microsoft Full-Stack Developer Professional Certificate — in progress (6/12 done, incl. Back-End Development with .NET and Database Integration and Management)
• Tecnólogo en Análisis y Desarrollo de Software (ADSO) — SENA
• Certified: Meta Back-End Developer · Microsoft (C# / .NET / Web / Blazor) · IBM (Django, Docker, Linux, DevOps)