Full Stack Engineer

The Opportunity

Build next-generation payment services in Elixir/Phoenix with ultra-low latency, high availability, and fault tolerance. Greenfield architecture, real business impact, full autonomy on technical decisions.

Stack: Elixir/Phoenix backend, HTML/CSS/vanilla JS frontend, AWS infrastructure

Requirements

Must-have

• Payments industry experience: Regulatory frameworks, including PCI. Payment processing systems including acquiring and/or issuing, with experience across the full transaction lifecycle—authorization, clearing, settlement, dispute management, and card network rules (Visa/Mastercard/AMEX).
• Strong backend development in any language (we'll teach Elixir)
• Web fundamentals: HTML, CSS, JavaScript
• API design & SQL databases
• Strong communication, autonomy, collaboration with distributed teams
• English: Intermediate to fluent

Nice to have

• Payment processor integrations (Stripe, Braintree, Authorize.net)
• Fraud prevention (3DS, risk scoring, chargebacks)
• AWS experience (EC2, Lambda, RDS)
• Concurrent/distributed systems knowledge
• AI integration into the SDLC

Bonus points

• Elixir/Phoenix or functional programming experience
• High-performance systems optimization

What You’ll Do

Core responsibilities

• Design/build payment services in Elixir/Phoenix (performance, reliability, maintainability)
• Integrate with processors, card networks, fraud detection, 3DS providers
• Optimize for approval rates, latency, and fault tolerance
• Collaborate on architecture, code reviews, and engineering standards
• Work within PCI DSS and card network compliance requirements

Your evolution

• Month 1: Fully onboarded, contributing to next-gen services, understanding payment flows and business impact
• Month 3: Working independently on features with guidance, solid architecture knowledge, shipping production code
• Month 6: Working autonomously on complex features, deep system understanding, trusted team contributor

About SeamlessPay

We're a payment optimization platform that helps businesses recover significant revenue lost to false declines, poor routing, and preventable chargebacks. We're building next-generation payment services in Elixir to achieve ultra-low latency, high availability, and fault tolerance at scale.

We're not just another payment gateway—we're the intelligence layer that sits above processors, making smarter real-time decisions through AI-powered routing, network tokens, 3D Secure, and dispute automation.

Compensation & Benefits

What we offer

• €60-75K annually based on experience (contractor via Deel)
• 100% remote, work from anywhere in Europe
• Flexible hours with core collaboration windows
• Unlimited time off (contractor model, aligned with local holidays)
• Greenfield architecture with modern stack
• High-impact work affecting company revenue
• Small team, big influence from day one

Ready to build next-gen payment infrastructure?

• If you're a payments expert who loves technical challenges and wants autonomy to do your best work, let's talk.