Freelancer profile translated to English.

Description

Backend Engineer specialized in fintech, payment gateways, and fraud prevention. I help you build and scale robust REST APIs, integrate payment providers like Stripe, and protect your business against fraudulent transactions — without sacrificing speed or regulatory compliance.

With over 3 years in production for fintech (Treew Inc.), I have led:

✓ Complete integrations of Stripe and other payment gateways

✓ Anti-fraud systems that blocked over $2M in illicit transactions

✓ Migrations from monolith to microservices without downtime

✓ Reduction of API latency by 40% through query optimization

✓ End-to-end PCI DSS compliance

Main Stack: Node.js, Python, TypeScript, PostgreSQL, MongoDB, Redis, Docker, AWS, Next.js, and React.

Certifications: AWS Certified Developer Associate · PCI DSS Compliance Specialist · Professional Scrum Master I.

What sets me apart: I combine solid backend engineering with deep knowledge of payments and compliance domains. I am not a generic backend dev — I understand what it means for a charge to fail in production, what a real fraud pattern looks like, and why a payment integration needs idempotent retries and full traceability.

Types of projects I deliver:

• Scalable and documented REST APIs (OpenAPI/Swagger)

• Integrations with payment gateways (Stripe, Redsys, etc.)

• Fraud detection and prevention systems

• Refactoring and migrations to microservices

• Backend performance and architecture audits

• Full-stack MVPs with Next.js + Node/Python

Available in Spanish and English. I work remotely from Madrid, with occasional availability for in-person meetings.

Languages

Spanish
Native or bilingual
English
Conversational

Workplace preferences

Remote only

Primarily works remotely

Treew Inc.
Backend Engineer
January 2022 - Today (4 years and 5 months)
Development of high-performance backend systems for fintech services. Reduction of API response time by 40% through query optimization. Implementation of a fraud prevention system that blocked over $2M in fraudulent transactions. Led the migration from monolith to microservices without downtime. Stack: Node.js, Python, PostgreSQL, Redis, Docker, AWS, Stripe, MongoDB.
Django FastAPI PostgreSQL Elasticsearch PCI DSS
Naroca
Junior Web Developer
January 2021 - January 2022 (1 year)
Development of enterprise web applications with Angular. Building responsive UI components and participating in code reviews. Stack: Angular, TypeScript, HTML, CSS, SCSS, Git.
Angular Front-End Development Typescript JavaScript QA testing