Software Developer - AI Focused

Location: Zagreb, CroatiaCompany DescriptionTrustap is a fintech start-up founded in Cork, Ireland. We provide payment solutions to a wide variety of different marketplaces and ecommerce stores. With offices in Ireland, Croatia, the UK, and the US, Trustap operates has partnerships in 27 different countries and collaborates with companies such as Stripe to deliver its market-leading product.This position is based in Zagreb, Croatia.The RoleWe are looking for a passionate Software Developer who will help build, maintain, and enhance the backend APIs for our high-traffic fintech platform. A major focus of this role will be developing the infrastructure and integrations for our new AI-driven transacting projects: ACP and UCP.This is an exciting opportunity for someone interested in building large-scale, secure microservices using best practices. You will bridge the gap between our core escrow platform, our partner solutions, and our cutting-edge transactional AI models. Applicants for this role should be passionate, creative, and confident in their ideas, while also being able to articulate those ideas clearly and apply constructive feedback in a collaborative environment.Expectations From You in This PositionAI System Integration: Work on our AI focused Agentic Commerce ensuring secure, low-latency data handoffs between the transactional AI and our backend.API Development: Maintain internal and public-facing REST APIs using semantic versioning to support first- and third-party clients.Microservices: Develop resilient services to be used in a microservices-based architecture, specifically designed to handle complex AI decision-making flows.Third-Party Integration: Integrate third-party tools, services, and dependencies with decoupling and fault-resilience in mind.Architecture & Infrastructure: Define builds, environments, and database migrations tailored to a scalable microservice environment.Documentation & Testing: Document APIs using formal (e.g., Swagger) and soft (user guide) formats, and write API “journey” tests that validate the lifecycle behavior of system objects.Teamwork: Collaborate actively within a cross-discipline team of software engineers, AI/Data specialists, and QA engineers.Minimum Qualifications (Must-Haves)Programming Experience: Strong backend experience with one of the following: PHP, Go, Java.Architecture & Design: Deep knowledge of modern OOP best practices, including SOLID principles, programming to interfaces, composition over inheritance, clean code, and linting.Tooling: Proficiency with package management, build tools, and versioning.Version Control: Strong proficiency with Git, including branching strategies, merging, and resolving conflicts across shared branches.API Fundamentals: Extensive experience developing REST APIs and a solid understanding of the semantics of HTTP, including verbs and resources.Bonus Qualifications (Nice-to-Haves)AI/ML Familiarity: Experience integrating backend systems with AI models, LLMs, or Python-based services.E-commerce Platforms: Familiarity with WordPress/Shopify plugin development and architecture.Frontend Knowledge: Familiarity with modern frontend frameworks, particularly React.Industry Experience: Previous experience working in the fintech, payments, or escrow field.Security First: Knowledge of backend security best practices, including SQL injection prevention, data sanitization, and DoS mitigation.Continuous Learning: A genuine enthusiasm to learn, evaluate, and implement new technologies as our AI capabilities expand.Why is it great to work in this position?ESOP programFlexible hoursEquipment orderingWFH 2 days in the week, 3 days from the officeBe at the ground level of building and launching Trustap’s first major AI-driven transaction products.