Full Stack Engineer

Senior Full Stack Engineer — Fintech, Node.js, TypeScript, AI/LLM Our client is an international fintech company that is actively scaling and developing its own payment products for the global market. The company builds technology solutions for payments, financial operations, integrations with banks and payment providers, internal automation, and product infrastructure. The team combines product development, fintech R&D, payment operations, engineering, and modern AI-native approaches to building software. We are looking for a strong Senior Full Stack Engineer who can work across backend and frontend, design scalable architecture, build reliable integrations, make independent technical decisions, and actively use AI tools in the development process. This is not just a classic full stack role. We are looking for an engineer who can contribute to fintech product development, payment-related systems, internal automation, AI/LLM integrations, and scalable web applications. Position Role: Senior Full Stack Engineer Focus: Node.js, TypeScript, Backend Architecture, Frontend Development, Fintech Integrations, AI/LLM Company type: International fintech company Product area: Payments, financial services, internal tools, automation, integrations Work format: Remote / flexible schedule Seniority: Senior / strong Senior Mission of the Role The main mission of this role is to help the company build and evolve reliable fintech products, scalable backend services, user-facing web applications, integrations with external systems, and AI-enabled internal tools. We are looking for a developer who can not only implement features, but also understand product and business goals, evaluate technical trade-offs, design clean architecture, support production-ready systems, and use AI tools to improve development speed, quality, and automation. Goals for the First 6 Months Understand the company’s fintech product architecture, business logic, payment flows, integrations, and development workflow. Take ownership of key backend and frontend areas of the product. Contribute to the design and development of scalable REST APIs and integrations with external services. Improve the quality, maintainability, and reliability of the codebase through refactoring, testing, code review, and technical documentation. Participate in designing authentication, authorization, user access, and secure data flow mechanisms. Actively use AI tools such as Claude Code, Codex, Cursor, GitHub Copilot, or similar tools to increase engineering productivity. Support the first AI/LLM-related integrations or internal automation initiatives. Identify technical bottlenecks and propose improvements in performance, security, architecture, developer experience, and scalability. Goals for 6–12 Months Become one of the key technical contributors in the engineering team. Own complex fintech features from architecture and implementation to testing and production support. Help standardize engineering best practices for backend, frontend, testing, API design, integrations, and AI-assisted development. Contribute to AI-enabled product features, internal engineering tools, or automation workflows. Improve the reliability, observability, performance, and security of production applications. Support the development of integrations with banks, payment providers, financial services, internal systems, or third-party APIs. Mentor less experienced engineers and help raise the overall engineering level of the team. Participate in long-term technical planning and product development strategy. Key Responsibilities Develop and maintain production-ready full stack web applications. Design, build, and support scalable backend services using Node.js and TypeScript. Design and implement REST APIs with proper versioning, error handling, backward compatibility, and clear API contracts. Develop frontend features using modern JavaScript / TypeScript and frameworks such as React, Next.js, Vue.js, or similar. Work with forms, validation, user input, DOM APIs, state management, and frontend performance. Design and implement integrations with third-party services, financial systems, payment-related APIs, and internal tools. Work with SQL databases, including schema design, complex queries, indexes, transactions, and query optimization. Implement secure authentication and authorization flows, including JWT, access / refresh tokens, OAuth 2.0, and role-based access control. Write and maintain unit, integration, and e2e tests. Participate in architecture discussions and technical decision-making. Conduct code reviews and help maintain a high-quality codebase. Analyze implementation complexity, technical risks, and possible trade-offs. Work closely with product managers, project managers, QA engineers, R&D specialists, payment operations, and other developers. Use AI tools to speed up development, improve code quality, generate technical ideas, support documentation, and automate routine engineering tasks. Integrate LLM APIs and AI-powered workflows into products or internal tools where relevant. Participate in improving CI/CD, Docker-based environments, monitoring, logging, and production diagnostics. Required Skills and Experience 5+ years of commercial experience as a Full Stack Developer / Full Stack Engineer. Strong experience with JavaScript and TypeScript. Deep knowledge of Node.js and experience building production-ready backend applications. Strong understanding of backend architecture and scalable application design. Experience with Express.js, NestJS, or similar Node.js backend frameworks. Strong experience with at least one modern frontend framework: React, Next.js, Vue.js, or similar. Strong understanding of HTML5, DOM API, forms, validation, and user input handling. Good understanding of frontend performance and web application life cycle. Experience designing and developing REST APIs. Understanding of API design, versioning, error handling, backward compatibility, and integration patterns. Practical experience integrating third-party services and external APIs. Good knowledge of SQL: database schema design, complex queries, indexes, transactions, and query optimization. Strong understanding of SOLID principles, separation of concerns, and common architecture patterns. Experience with authentication and authorization mechanisms: JWT; access / refresh tokens; OAuth 2.0; role-based access control. Experience writing and maintaining unit, integration, and e2e tests. Understanding of application testing strategy. Understanding of Web Security principles, including OWASP Top 10. Experience with Docker and understanding of containerization. Basic understanding of CI/CD processes. Ability to make independent technical decisions and explain architectural or technology choices. Experience with code review and maintaining code quality. Good written and spoken English communication skills. AI Engineering Requirements Practical experience using AI tools for software development, such as Claude Code, Codex, Cursor, GitHub Copilot, or similar. Good prompt engineering skills and understanding of how to work effectively with LLMs. Practical experience integrating LLM APIs into applications. Understanding of MCP — Model Context Protocol — and possible scenarios of its use. Understanding of approaches to building AI agents, using tools, and integrating LLMs with external systems. Interest in AI-assisted development, automation, internal tools, and AI-enabled product features. Ability to use AI tools not only for code generation, but also for debugging, documentation, testing, refactoring, architecture research, and productivity improvement. Fintech Experience Will Be a Strong Advantage Experience working in fintech, payments, banking, crypto, e-commerce, financial services, or product companies. Understanding of payment flows, transaction processing, payment providers, banking integrations, reconciliation, or financial operations. Experience building secure systems that process sensitive user, financial, or operational data. Experience integrating multiple external services within one product. Understanding of compliance-sensitive environments and security-first engineering culture. Experience working with internal tools for operations, finance, payments, risk, support, or analytics. Will Be a Plus Experience with React, Next.js, Vue.js, Redux, or similar frontend technologies. Experience developing or integrating MCP servers / clients. Experience building production-ready RAG systems. Experience with queues, background jobs, and asynchronous data processing. Understanding of caching and experience with Redis or similar solutions. Experience with monitoring, logging, and production diagnostics. Basic or intermediate DevOps knowledge. Practical experience with Docker / Docker Compose. Experience setting up CI/CD pipelines using GitHub Actions, GitLab CI, or similar tools. Experience with Linux, basic server administration, and troubleshooting. Understanding of Nginx / reverse proxy, DNS, SSL/TLS, and HTTPS. Experience with cloud infrastructure such as AWS, GCP, Azure, or similar. Basic understanding of Kubernetes. Experience with Python, Java, . NET, PHP, Golang, or other backend technologies. Experience mentoring less experienced engineers. What We Offer Long-term cooperation with an international fintech company. Opportunity to work on own fintech products and payment-related solutions. Fully remote work format and flexible schedule. Large-scale international product development. Direct impact on product architecture, engineering quality, automation, and internal tools. Opportunity to work with modern AI tools, LLM integrations, and AI-assisted development workflows. Collaboration with product, engineering, R&D, payment operations, and business teams. Competitive compensation based on experience and technical level. Strong opportunities for professional growth. A team where ownership, strong technical thinking, initiative, and business-oriented engineering are valued. Who This Role Is For This role is a strong fit for a Senior Full Stack Engineer who is confident in backend and frontend development, understands architecture, security, testing, databases, and integrations, and wants to grow in fintech, AI Engineering, LLM APIs, MCP, AI agents, and modern AI-assisted development workflows. We are looking for someone who can take ownership, think independently, communicate clearly, and help build reliable, scalable, secure, and maintainable fintech products.