Carlos Sebastian Castañeda

Carlos Sebastian Castañeda

Senior Software Engineer

Startup | Fintech | Crypto | Digital Banking | AI | BTC

Valencia, Spain

About

Software Engineer with over 10 years of experience building production systems across FinTech, crypto, government, and health-tech domains.

My strengths

  • Strong backend foundation in Python (Django, FastAPI), AWS, and Docker
  • Hands-on experience delivering customer-facing web applications and REST APIs end to end
  • Full ownership of features — from system architecture and payment integrations to frontend delivery, security remediation, and cross-functional collaboration with Product, Security, and DevOps teams
  • Fast learner who adapts quickly to new tech stacks and tooling as project needs evolve

My tech stack

Languages & Frameworks

Python JavaScript TypeScript Java Django FastAPI Flask Spring Boot Nodejs Astro

Data & Infrastructure

PostgreSQL MySQL MongoDB Redis AWS Terraform Docker Kubernetes Git

Observability & DevOps

New Relic Datadog Sentry PagerDuty GitHub Actions Coralogix

Tools & AI

Postman JIRA Confluence Figma GitHub Copilot Claude Code OpenCode Gemini Codex

Experiences

2021-2026

Senior Software Engineer · Xapo Bank

Senior Backend Engineer in different company areas and teams.

  • Architected and shipped integrations with multiple FIAT and crypto payment providers using Python and AWS, enabling secure transaction processing for 10K+ customers.
  • Built and deployed internal automation tools that reduced manual operations by around ~50%, streamlining processing workflows across banking operations.
  • Owned the security alert pipeline for the team — reviewing and remediating dependency vulnerabilities, enforcing secret scanning, and preventing sensitive data leaks in version control and application logs.
  • Python
  • Java
  • Docker
  • AWS
  • JavaScript
  • Terraform
  • NewRelic
  • Coralogix
  • Django
  • FastAPI
  • PostgreSQL
  • MySQL
  • Redis

2018-2021

Senior Software Engineer · AccelOne

Senior Software Engineer for Xapo Bank and Seattle Children's Hospital, Foundation, and Research

  • Developed internal tooling for XAPO Bank (as external consultant) using Python, Flask, and MongoDB, supporting operational workflows for high-volume FIAT and cryptocurrency transaction processing.
  • Designed and built a REST API using Node.js for a health-tech mobile application to track and manage medical procedure data, deployed on AWS.
  • Python
  • Flask
  • Nodejs
  • MongoDB

2016-2018

Software Engineer · DevsAr

Software Engineer for Moni and Matterport

  • Built and enhanced features for Matterport's customer-facing web portal using Python (Django) on the backend and JavaScript on the frontend, working on-site with the engineering team in San Francisco, CA.
  • Implemented a 3D model cloning feature in the customer portal, allowing users to duplicate and manage spatial models directly from the web interface.
  • Shipped customer-facing features for a high-traffic payday loan platform serving 5K+ users, built with Python (Django, Celery) on the backend and JavaScript (Marionette) on the frontend.
  • Enhanced the internal operations dashboard, improving loan management workflows and giving the operations team better visibility into portfolio health and borrower status.
  • Python
  • Django
  • Datadog
  • JavaScript

Certifications

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Academic

2018

Computer Graphics, Images and Computer Vision Specialist [M.Sc.]

Universidad Nacional de la Plata, Postgrado - Facultad de Informática - UNLP | Argentina

2010

Licenciado [B.Sc.] en Informática

Universidad Nacional de la Plata, Facultad de Informática - UNLP | Argentina

2004

Analista de Computación

Universidad Nacional de la Plata, Facultad de Informática - UNLP | Argentina