> Markdown version of [/jobs/ext/1926403-senior-fullstack-engineer-customer-portals-apis](https://www.wearedevelopers.com/jobs/ext/1926403-senior-fullstack-engineer-customer-portals-apis). Every page supports `.md` or `Accept: text/markdown`. Links point to the HTML versions so they work for humans too. Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md).

---

# Senior Fullstack Engineer - Customer Portals & Apis

- **Company:** Factorial
- **Location:** Madrid, Spain
- **Contract:** Permanent contract
- **Skills:** Application Programming Interfaces (APIs), Interaction Design, Ruby on Rails, Backend, Api Design
- **Published:** August 5, 2026
- **Apply:** https://www.buscojobs.com.es/senior-fullstack-engineer-customer-portals-apis-en-madrid-ID-365574014

## About the Role

The role involves designing systems that integrate internal platforms while improving user interactions.
Ideal candidates have 5+ years of backend or full-stack experience, strong skills in API development and user experience with a focus on reliability.
Join us to contribute to cutting-edge business management technology.
#J-*****-Ljbffr

## Description

Factorial is hiring a Fullstack Engineer in Barcelona to build scalable user experiences and customer-facing portals.You'll work in a collaborative environment with a team of over 250 developers, using Ruby on Rails and React.The role involves designing systems that integrate internal platforms while improving user interactions.Ideal candidates have 5+ years of backend or full-stack experience, strong skills in API development and user experience with a focus on reliability.Join us to contribute to cutting-edge business management technology.#J-*****-Ljbffr


## Related Videos

- [API Design - Getting Started](https://www.wearedevelopers.com/videos/33-api-design-getting-started)
- [Next Level Enterprise Architecture: Modular, Flexible, Scalable, Multichannel and AI-Ready?](https://www.wearedevelopers.com/videos/1017-next-level-enterprise-architecture-modular-flexible-scalable-multichannel-and-ai-ready)
- [Coffee with Developers: David Heinemeier Hansson](https://www.wearedevelopers.com/videos/875-coffee-with-developers-david-heinemeier-hansson)
- [Developing the Backend with Stefan Lingler, CTO at Shpock](https://www.wearedevelopers.com/videos/100360-developing-the-backend-with-stefan-lingler-cto-at-shpock)
- [Meet Your New BFF: Backend to Frontend without the Duct Tape](https://www.wearedevelopers.com/videos/682-meet-your-new-bff-backend-to-frontend-without-the-duct-tape)
- [Rest API Antipatterns](https://www.wearedevelopers.com/videos/100208-rest-api-antipatterns)

## Related Articles

- [The 7 Most Popular Backend Frameworks for Developers](https://www.wearedevelopers.com/magazine/403-the-7-most-popular-backend-frameworks-for-developers)
- [Find a Developer Job: 12 Best Job Sites For Developers](https://www.wearedevelopers.com/magazine/165-find-a-developer-job-12-best-job-sites-for-developers)
- [Fully Remote Software Engineer Jobs](https://www.wearedevelopers.com/magazine/447-fully-remote-software-engineer-jobs)
- [Why Upskilling And Reskilling is Important For Developers](https://www.wearedevelopers.com/magazine/428-why-upskilling-and-reskilling-is-important-for-developers)
- [Is Software Engineering Over-Saturated?](https://www.wearedevelopers.com/magazine/418-is-software-engineering-over-saturated)
- [Where To Find Software Engineering Jobs](https://www.wearedevelopers.com/magazine/396-where-to-find-software-engineering-jobs)