Sr. Fullstack Engineer

About Tereina

Tereina is on a mission to revolutionize B2B payments. We are a well-funded, early-stage startup building cutting-edge solutions that transform how businesses move money. Our platform handles cross-border payment processing, counterparty management, bank account administration, and compliance workflows for eterprise customers worldwide.

We are building a modern portal application using a service-oriented architecture with Spring Boot microservices, a Spring Boot BFF (Backend for Frontend), and a custom frontend built with SAP UI5 Web Components, React and TypeScript. We are currently evolving our UX with a clean, data-rich design language focused on advanced search, tabular data views, and dashboard analytics.

About the Role

As a Senior Fullstack Engineer, you will be a key technical leader responsible for shaping the user experience of the Tereina Portal. You will own the frontend architecture, drive the implementation of our new design system, and work across the full stack to ensure our UX vision is realized with production-quality code. You will partner closely with product, design, and backend engineers to deliver enterprise-grade interfaces for payment operations, counterparty management, and compliance with workflows.

This role demands deep expertise in modern frontend technologies, a strong eye for design quality, and the ability to influence architecture decisions across the portal and its supporting BFF layer. You will mentor other engineers on UX best practices and help define our standards for accessibility, performance, and component reusability.

Key Responsibilities

Framework Development

These are the responsibilities focused on building the underlying systems, architecture, and shared infrastructure:

• Frontend Architecture: Own and evolve the frontend architecture of the Tereina Portal, including the component library, state management patterns, and data-fetching layer built on our existing frontend infrastructure.

• Design System Implementation: Lead the implementation of our evolving design system, translating UX designs into reusable, accessible components using SAP UI5 Web Components and TypeScript. Establish patterns for dashboards, data tables, search interfaces, and detail views.

• BFF Collaboration: Work closely with the BFF layer (Spring Boot) to shape API contracts, optimize data-fetching patterns, and ensure the portal proxy controllers deliver exactly what the frontend needs. Influence the design of search proxy endpoints and OpenAPI specifications.

• Performance & Accessibility: Champion frontend performance optimization (lazy loading, caching strategies, efficient re-renders) and WCAG accessibility standards across all portal views.

Rollout & Adoption

These are the responsibilities focused on shipping features, driving usage, and working across teams:

• Search & Data Views: Architect the frontend implementation of our new standardized search framework, integrating table-based server-side pagination, sorting, and filtering via our REST filter contracts. Implement column configuration, saved searches, and spreadsheet exports.

• Dashboard & Analytics UX: Build rich, interactive dashboard experiences including payment summaries, held-payment alerts, trend charts, and failure-analysis views.

• Implement data visualizations that surface actionable insights for enterprise payment operations.

• Cross-Functional Leadership: Partner with Product, Design, and Platform teams to translate business requirements into UX solutions. Drive UX technical decisions and advocate for user experience quality in architectural discussions.

• Mentorship: Mentor mid-level and junior engineers on frontend best practices, code quality, component design, and UX engineering principles. Lead code reviews, establish coding standards, and help shape the engineering culture as the team grows.

Required Qualifications

• 7+ years of software engineering experience with a strong focus on frontend development and UX engineering

• Expert proficiency in TypeScript and modern JavaScript.

• Expert-level React experience, including deep knowledge of hooks, state management patterns, and component architecture, with a track record of building complex, data-rich web applications

• Hands-on experience with headless table libraries (TanStack Table preferred) including server-side pagination, sorting, and filtering

• Proven ability to build responsive, accessible (WCAG 2.1 AA) interfaces for enterprise applications

• Experience with BFF (Backend for Frontend) patterns and REST API integration, including OpenAPI-generated clients

• Solid understanding of authentication flows (OAuth2/OIDC, session-based auth) and security best practices (CSRF, CSP)

• Experience with AI agent frontends — streaming UI, conversation management, and integration with Spring AI, LangChain, or MCP backends

• Experience with data visualization libraries and building dashboard interfaces with charts and analytics components

• Strong system design skills with the ability to influence architecture decisions across frontend and API layers

• Excellent communication skills and experience collaborating in cross-functional agile teams

• Professional fluency in English (written and verbal) is required; all engineering collaboration, documentation, code reviews, and stakeholder communication are conducted in English

Preferred Qualifications

• Experience with SAP UI5, SAP UI5 Web Components, or enterprise UI frameworks in regulated industries

• Familiarity with Spring Boot BFF architectures and Java/Kotlin backend services

• Background in fintech, payment processing, or B2B financial platforms

• Experience with SheetJS or similar client-side data export libraries

• Knowledge of JPA Specifications or similar backend query patterns and how they map to frontend filter UIs

• Experience building multi-tenant SaaS applications with organization-scoped data access

• Track record of leading frontend architecture decisions and establishing engineering standards

Why Join Tereina?

• Shape the Product: Own the UX of a platform that processes millions in B2B payments.

• Your work directly impacts how enterprise customers manage counterparties, execute payments, and maintain compliance.

• Technical Voice: Your opinions on API design, BFF contracts, and component architecture will directly influence how our stack is built. You won't just consume APIs – you'll help shape them.

• Modern Stack: Work with a thoughtfully chosen technology stack that values simplicity and pragmatism over hype. We adopt new tools where they add real value.

• Early-Stage Impact: Join a well-funded startup where your contributions shape both the product and the engineering culture from the ground up.

• Full-Stack Exposure: Collaborate across the entire stack, from frontend components to BFF orchestration to backend service APIs.

• AI-Forward Culture: We embrace AI as a tool for innovation and efficiency. We are looking for team members who are curious, adaptable, and excited to leverage AI in their work.

• Team & Growth: Work with a collaborative, diverse team that values technical excellence, continuous learning, and work-life balance.

Ready to Apply?

If you're passionate about building performant, secure, and user-friendly web applications and want to shape the future of payments technology, we'd love to hear from you.

Tereina embraces AI as a tool for innovation, efficiency, and growth. We're looking for team members who are curious, adaptable, and excited to leverage AI in their work—no matter the role. Tereina is an equal opportunity employer committed to diversity and inclusion.

Originally posted on Himalayas