Full Stack Engineer

The OpportunityBuild 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 infrastructureRequirementsMust-havePayments 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, JavaScriptAPI design & SQL databasesStrong communication, autonomy, collaboration with distributed teamsEnglish: Intermediate to fluentNice to havePayment processor integrations (Stripe, Braintree, Authorize.net)Fraud prevention (3DS, risk scoring, chargebacks)AWS experience (EC2, Lambda, RDS)Concurrent/distributed systems knowledgeAI integration into the SDLCBonus pointsElixir/Phoenix or functional programming experienceHigh-performance systems optimizationWhat You’ll DoCore responsibilitiesDesign/build payment services in Elixir/Phoenix (performance, reliability, maintainability)Integrate with processors, card networks, fraud detection, 3DS providersOptimize for approval rates, latency, and fault toleranceCollaborate on architecture, code reviews, and engineering standardsWork within PCI DSS and card network compliance requirementsYour evolutionMonth 1: Fully onboarded, contributing to next-gen services, understanding payment flows and business impactMonth 3: Working independently on features with guidance, solid architecture knowledge, shipping production codeMonth 6: Working autonomously on complex features, deep system understanding, trusted team contributorAbout SeamlessPayWe'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 EuropeFlexible hours with core collaboration windowsUnlimited time off (contractor model, aligned with local holidays)Greenfield architecture with modern stackHigh-impact work affecting company revenueSmall team, big influence from day oneReady 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.