Sr Software Engineer; Frontend Focus, Brazil

Kard is transforming customer loyalty with our rewards-as-a-service API platform. We empower our partners, from neobanks to financial institutions and beyond, to offer tailored rewards that celebrate customers' daily transactions. Backed by $30M from industry-leading investors and seasoned experts, we are reshaping the future of customer engagement.

Design, build, and refine the frontend systems that power Kard's transaction-linked rewards platform. You will craft interfaces that serve our partners and their customers—performant, accessible, and built to last. The role is centered on React and Type Script in an AWS environment, with backend work in Go, contributing to a flexible, full-stack experience.

Working closely with product, design, data, and other engineering teams, you will shape the frontend architecture, establish standards, and champion quality. You'll collaborate to turn product vision into reality—not just executing designs, but helping shape them. At Kard, we value engineers who are business thinkers, pragmatic problem solvers, and strong communicators. Whether refining component systems, improving test coverage, mentoring teammates, or leading a feature from canvas to production, you will have a direct impact on our technology and customers.

This role leans frontend—roughly 70/30—but you'll contribute across the stack when the work calls for it.

• Design and implement frontend systems in React and Type Script , with attention to performance, accessibility, and maintainability.
• Own the front of the frontend
  : design tokens, CSS architecture, and the tooling that makes styling scalable and consistent.
• Establish and evolve testing practices that catch real bugs without creating brittleness—favoring tests that support refactoring over tests that fight it.
• Contribute to backend services in Go
  , building APIs and integrations that support frontend needs.
• Collaborate with product, design, and engineering to shape features from early concept through delivery, building in narrow vertical slices that deliver value continuously.
• Drive frontend architecture decisions
  , balancing trade-offs between developer experience, optionality, performance, and business impact.
• Improve automation, CI/CD, and observability for frontend systems, enabling faster iteration and more reliable releases.
• Mentor engineers and establish standards
  —proposing them quickly, building consensus, shipping them, and evolving them thoughtfully when circumstances change.

• Expert-level React and Type Script , with well-informed, contextualized opinions on ecosystem choices—when to reach for external state management, which patterns scale, what to avoid.
• Deep appreciation for the craft of frontend development
  : CSS (and tools for managing it), design systems, accessibility, and the details that make interfaces feel right.
• Strong linting and testing philosophy and practice
  —experience with Vitest, Playwright or Cypress, and an understanding of what makes frontend tests reliable rather than flaky. Bonus if you have thoughtful opinions on Visual Regression Testing.
• Comfort working within Docker, Terraform, and Kubernetes environments. You don't need to be a Dev Ops specialist, but you can be productive within established patterns.
• Experience building REST APIs
  , with an understanding of how frontend and backend responsibilities should be divided.
• Business-minded approach to engineering
  : you deliver in vertical slices, you understand why features matter, and you collaborate with product and design to shape outcomes—not just implement specs.
• Strong communication and collaboration skills
  , with experience working on small teams and mentoring other engineers.
• Proficiency with AI-assisted development tools like Claude Code—you see them as complementary to your expertise, guide them critically, and integrate them into your craft.

• Experience with Go
  , or genuine interest in learning it.
• Background with GraphQL or Backend-for-Frontend patterns.
• Experience with mobile, especially Webview
  .
• Experience with Databricks, Mongo
  
  DB, or PostgreSQL
  .
• Background in fintech, adtech, or transaction-based systems
  .
• Contributions…