Senior Backend Engineer - Payment Venture

About the Company

Project Y is hiring on behalf of Fluxmap.io, a venture-backed fintech startup founded by former Stripe and Adyen managers based in Amsterdam and Dublin.
Fluxmap is on a mission to become the single source of truth for payment fees, helping platforms and marketplaces gain complete visibility into their payment processing costs, design smarter payment strategies, and streamline financial operations.

The platform is already live on the Stripe App Marketplace, with early design partners using it to run their payments businesses on autopilot, leveraging AI to optimise costs, boost revenue, and cut manual work.
The founding team is now looking for a Senior Backend Engineer to help take their MVP to the next level. This is a high-impact role with the potential to evolve into a Founding Engineer position.

Key Responsibilities

• Own & Scale the System: Lead backend development (TypeScript, PostgreSQL, AWS) with a focus on scalability, performance, and reliability.

• Deliver Customer-Facing Features: Work closely with fast-growing SaaS platforms to translate payment insights into powerful product features.

• Data Integrations: Build and maintain integrations with Stripe, Adyen, Checkout.com, and other PSPs — normalizing large volumes of payment data.

• Accelerate with AI: Use AI-assisted development tools (Cursor, GitHub Copilot, OpenAI APIs) to shorten delivery cycles and increase output.

• Full-Stack Collaboration: While backend is your core focus, contribute to React-based frontend features when needed to ensure seamless user experiences.

• Work Directly with Founders: Collaborate closely with the CTO and CEO on architecture, technical decisions, and roadmap planning.

Must-Haves

• 5+ years of backend engineering experience, ideally within startups or SaaS environments.

• Proficiency in TypeScript (NestJS), PostgreSQL, and AWS (S3, K8, SQS etc.).

• Experience designing and maintaining scalable APIs and data-intensive systems.

• Deep understanding of payment systems (e.g. Stripe, Adyen, PayPal) or fintech products.

• Strong communication skills and the ability to work autonomously in a fast-paced environment.

• Passion for building and experimenting with AI-assisted workflows (Cursor, Copilot, OpenAI etc.).

Nice-to-Haves

• Prior experience in fintech, analytics, or financial operations.

• Familiarity with modern data processing pipelines and ETL design.

• Product mindset, able to connect technical decisions to user and business value.

• Interest in scaling early-stage infrastructure into a mature production system.