I’m a Barcelona-based Senior Front-end & Mobile Engineer with 9 years’ experience shipping React Native and React apps from zero-to-one and beyond. I’ve led green-field builds for VC-backed startups (Fluz, BodeBoca, VetEasy) and most recently owned the mobile/web code-base at Laurel Gaming and my own venture, Divenamic. My focus is clean architecture, high-performance UX, automated CI/CD, and close collaboration with product & design to get features in users’ hands fast.…

Guillermo Sierra

I’m a Barcelona-based Senior Front-end & Mobile Engineer with 9 years’ experience shipping React Native and React apps from zero-to-one and beyond. I’ve led green-field builds for VC-backed startups (Fluz, BodeBoca, VetEasy) and most recently owned the mobile/web code-base at Laurel Gaming and my own venture, Divenamic. My focus is clean architecture, high-performance UX, automated CI/CD, and close collaboration with product & design to get features in users’ hands fast.…

Available to hire

I’m a Barcelona-based Senior Front-end & Mobile Engineer with 9 years’ experience shipping React Native and React apps from zero-to-one and beyond. I’ve led green-field builds for VC-backed startups (Fluz, BodeBoca, VetEasy) and most recently owned the mobile/web code-base at Laurel Gaming and my own venture, Divenamic. My focus is clean architecture, high-performance UX, automated CI/CD, and close collaboration with product & design to get features in users’ hands fast.

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Skills

Experience Level

React Native
Expert
React JS
Expert
Node.js
Expert
Kotlin
Expert
TypeScript
Expert
GraphQL
Intermediate
Swift
Intermediate
AWS
Intermediate
Python
Intermediate

Language

Spanish; Castilian
Fluent
Catalan; Valencian
Fluent
English
Advanced
French
Intermediate

Work Experience

Senior Mobile Developer at DopeList
May 1, 2025 - Present
Developed a React Native Web platform featuring AI-powered content enrichment and coordinated team efforts to deliver scalable solutions.
Senior Front-end & Mobile Dev at Laurel Gaming
March 31, 2025 - July 14, 2025
Built Next JS 14 and React Native based gaming marketplace with real-time multiplayer features and created a custom UI kit.
Senior Mobile Developer at BodeBoca
February 29, 2024 - July 14, 2025
Led the re-platforming of Spain’s leading wine e-commerce app using React Native, TypeScript, and GraphQL.
Senior Mobile Engineer at Fluz
October 31, 2023 - July 14, 2025
Worked on a cash-back FinTech app, developing new wallet and rewards flows on a React Native codebase.
Senior Mobile Developer at eevie GmbH
May 31, 2023 - July 14, 2025
Developed a climate-engagement SaaS app using React Native and GraphQL; delivered a habit-tracking module.
Senior Mobile Developer at Doctoralia / DocPlanner
September 30, 2022 - July 14, 2025
Main owner of the Doctors app, responsible for design-system analytics and doubling monthly active users.
React Native Developer at Holded
November 30, 2020 - July 14, 2025
Built CRM and POS mobile suites, managing state with MobX and maintaining CI pipelines.
CTO & Co-Founder at goPure
September 30, 2019 - July 14, 2025
Led a 4-developer team building a Nutrition SaaS MVP using React Native, Node.js, and AWS.
Android & React Native Dev at Velocity Black
March 31, 2018 - July 14, 2025
Migrated luxury-concierge Android app to React Native, improving the release cadence.
Java Developer (R&D) at Amadeus IT Group
November 30, 2016 - July 14, 2025
Prototyped merchandising engines in Java/Spring for airline clients.
Android Developer (Contract) at SEAT
May 31, 2016 - July 14, 2025
Developed NFC proof-of-concept for in-vehicle sensor data using Java and Android SDK.

Education

B.Sc. at UPC Barcelona
January 1, 2010 - December 31, 2015

Qualifications

Add your qualifications or awards here.

Industry Experience

Software & Internet, Gaming, Financial Services, Retail, Healthcare, Telecommunications

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