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# Backend developer

- **Company:** Bjak
- **Location:** Madrid, Spain
- **Salary:** €52,000.0 - €104,000.0
- **Contract:** Permanent contract
- **Skills:** Application Programming Interfaces (APIs), Artificial Intelligence, User Authentication, Databases, Data Integrity, Software Debugging, Systems Integration, Backend, AI Platforms, Low Latency, Front End Software Development
- **Published:** July 17, 2026
- **Apply:** https://www.adzuna.es/contact-us.html

## About the Role

+ Strong backend engineering experience in production systems.
 + Good understanding of APIs, databases, authentication, authorization, queues, jobs, events and integrations.
 + Experience building services used by real customers or internal operations at meaningful scale.
 + Strong debugging, reliability, security and data quality mindset.
 + Able to make practical trade-offs between speed, correctness, scalability and maintainability.
 + Fintech, payments, banking, wallet, KYC, fraud or risk experience is a strong plus, but not required if fundamentals are strong., English is our main working language across global teams. Strong English communication is required.

## Description

We are looking for backend engineers to build the core systems behind BJAK's AI Neobank app.
This role is for engineers who can build reliable APIs, workflows and financial product infrastructure that can scale across markets, partners and millions of users.

What You'll Own

 + Build backend services and APIs for onboarding, accounts, payments, cards, transfers, rewards, travel, FX, KYC and risk flows.
 + Design reliable systems that can support real customer transactions, operational workflows and future financial products.
 + Integrate with internal systems, financial partners, payment providers, AI services and third-party platforms.
 + Own backend quality across reliability, security, latency, observability, data integrity and incident handling.
 + Work with product, frontend, mobile and AI teams to launch features quickly and safely.
 + Improve existing systems by simplifying flows, removing manual work and automating repeatable processes., + Engineers who only want isolated backend tasks.
 + People who ignore security, data consistency, monitoring or operational risk.
 + Developers who cannot work with fast-changing product requirements.
 + Candidates who talk about scale but have not handled production systems.
 + People who exaggerate impact without being clear on ownership.

The Bar
We are looking for engineers with real technology career highlights. A strong highlight is not just working at a famous company. A strong highlight means you personally helped build, ship or scale a serious product, platform or system.


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