Senior Backend Software Engineer - Consumer Banking

At Scalapay, we’re shaping a culture with high standards, independent and critical thought, innovation, ownership, and continuous learning . We operate in a fast-moving, tech-driven environment , and we’re looking for people who thrive in change, think boldly, and take initiative.

If you’re ready to put your potential to the test in a hiring process designed to spotlight exceptional talent, this is your chance to stand out and grow with one of Europe’s most ambitious fintech teams .

#MakeItHappen #PlayAsATeam #StayCurious #FocusOnCustomer.

The Mission

Scalapay is an AI-first international fintech. We're looking for a Backend Software Engineer with banking platform experience to join our Consumer Banking team. You'll design and deliver high-performance, secure and scalable APIs that power our customer experience. You'll work spec-first: you define what good looks like, and AI coding agents help you build it faster without lowering the bar on quality, security or compliance.

Key Responsibilities:

AI-First Engineering

Write clear specifications and technical designs that AI coding agents (e.g. Claude Code) implement from, then direct, review and test their output;

Take full ownership of AI-generated code, making sure it meets our standards for security, performance and PCI DSS compliance before it ships;

Use AI across the whole development lifecycle: test generation, code review, documentation, debugging and incident analysis;

Help shape the team's AI tooling, shared context, prompts and guardrails so that development becomes more automated over time.

API Development & Integration

Design, build and maintain high-quality REST APIs using NestJS and TypeScript;

Meet performance targets of under 200ms response time through caching, query optimisation, payload compression, rate limiting, pagination and filtering;

Integrate with external services and banking partners, keeping the platform resilient to third-party failures.

Architecture

Build scalable, maintainable microservices using dependency injection, modular design and clean code principles;

Develop event-driven systems and real-time features.

Security & Compliance

Implement authentication and authorisation (JWT, OAuth2, MFA) and API security measures (TLS, API key management, request signing);

Apply secure coding practices, including input validation and protection against SQL injection and XSS;

Ensure PCI DSS compliance and encryption of sensitive data at rest and in transit.

Data & Infrastructure

Design efficient MySQL/PostgreSQL schemas, manage migrations and optimise queries and indexing;

Deploy on AWS with Docker, EKS, and CI/CD pipelines, working with DevOps on infrastructure requirements;

Monitor system performance through logging, tracing and alerting.

Required Qualifications

5+ years of backend development experience, including banking platforms, system integrations and ledgers

3+ years with NestJS and TypeScript, or comparable frameworks and languages

Proven AI spec-driven development: you've shipped production software by specifying, directing and validating the work of AI coding agents

Strong MySQL and/or PostgreSQL skills: schema design, query optimisation and indexing

Deep knowledge of REST API design, plus GraphQL experience (code-first and schema-first)

Track record of finding and fixing API performance bottlenecks, including caching (Redis, Memcached, HTTP caching)

Strong API security background: authentication, authorisation, encryption, security testing and vulnerability assessment

Experience with AWS (EC2, RDS, Lambda, API Gateway, CloudWatch) or a comparable cloud platform

Solid testing practice (Jest, unit and integration testing), Git workflows and agile delivery

What We're Looking For

Banking platform experience. You’ve built or worked on banking systems, including system integrations and ledgers.

An AI-first builder. You can show us AI projects that demonstrate your spec-driven wa