Senior Fullstack Engineer (Kotlin/React) at Kunai

Key Facts

Remote From:

United States

Full time

Senior (5-10 years)

English

Hard Skills

Other Skills

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Reliability
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Collaboration
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Communication
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Teamwork
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Problem Solving

Roles & Responsibilities

5+ years of experience in full-stack software engineering within complex, enterprise environments.
Strong backend development experience using Kotlin and production-grade microservices with Spring Boot.
Hands-on experience with AWS cloud infrastructure, containerized workloads, and Amazon ECS.
Strong frontend development experience with React and TypeScript, plus proficiency in modern JavaScript and GitHub-based workflows.

Requirements:

Design, develop, and maintain secure, high-performance backend services using Kotlin and Spring Boot within a microservices architecture.
Build and maintain modern, accessible front-end interfaces using React and TypeScript.
Develop and maintain RESTful APIs with enterprise-grade scalability, reliability, and security; deploy and monitor containerized workloads on AWS ECS.
Collaborate with cross-functional teams, participate in architectural reviews, optimize relational databases (PostgreSQL/MySQL), and ensure secure coding and governance compliance.

Kunai

Information Technology & Services

About Kunai

Kunai Co. is a team of developers, designers, and product managers building seamless customer experiences that unite digital products with FinTech. Kunai concepts, designs, and develops unique digital products and payment experiences for the world's top companies. Starting in 1999, Kunai helped Cisco Systems prepare for Y2K, and then in 2006, built the world's first touchscreen PC. Later, Kunai designed and developed some of the world's first successful iOS apps. With Capital One’s acquisition in 2015, we focused on fintech and how to build on a massive scale, so a portion of our team rebranded as Kunai and continued to refine our approach to product development. Over 20 years, Kunai shipped over 150 digital products that are trusted by Fortune 500 companies and unicorn startups alike. Kunai's founders, being former bank executives, started the company with the insights of years-long struggles to hire developer talent. As a result, only the top 3% of developers worldwide make it onto a Kunai team. What we do: Technical Staffing: The Kunai Direct Sourcing Platform helps companies to find, vet, interview, and onboard the world’s best developers. Kunai works on a range of technologies and platforms and has deep experience in fintech and leverages industry-leading APIs and practices. Digital product development for fintech: Kunai understands the unique needs of financial services companies. We're a digital product development consultancy focused on fintech. Kunai handles product management, design, development, cloud management, and much more to build your next new idea into a prototype faster. We build long-term relationships with our clients. Our portfolio includes all four major payment networks, four top ten US banks, seven Fortune 500 technology companies, and ten unicorn startups. If you have an idea and need a team that can make it a reality, we should talk.

Company type: Scaleup

Industry: Information Technology & Services

Founded: 2018

Company size: 201 - 500

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Job description

Kunai builds full-stack technology solutions for banks, credit and payment networks, infrastructure providers, and their customers. Together, we are changing the world’s relationship with financial services. At Kunai, we help our clients modernize, capitalize on emerging trends, and evolve their business for the coming decades by remaining tech-agnostic and human-centered.

Overview

We are seeking a Senior Fullstack Engineer to support the design and delivery of secure, scalable, enterprise-grade applications within a large financial services environment. This role will be instrumental in modernizing and enhancing cloud-native platforms that power critical banking systems.

The ideal candidate brings deep expertise in Kotlin and Spring Boot, strong frontend capabilities with React and TypeScript, and hands-on experience operating containerized applications in AWS. This position requires a strong understanding of system reliability, security best practices, and performance optimization within highly regulated, large-scale environments.

Key Responsibilities

Design, develop, and maintain secure, high-performance backend services using Kotlin and Spring Boot within a microservices architecture.
Build and enhance modern, responsive user interfaces using React and TypeScript, ensuring accessibility and maintainability.
Develop and maintain RESTful APIs that meet enterprise standards for scalability, reliability, and security.
Deploy, manage, and monitor containerized applications using Amazon ECS (Elastic Container Service).
Leverage core AWS services to design resilient, fault-tolerant cloud infrastructure aligned with enterprise architecture standards.
Design, implement, and optimize relational database solutions using PostgreSQL and/or MySQL, including complex query development and performance tuning.
Follow structured Git-based workflows using GitHub, including feature branching, pull request reviews, and controlled release processes.
Ensure adherence to secure coding standards, compliance requirements, and enterprise governance frameworks.
Identify and resolve system performance issues across application, database, and infrastructure layers.
Participate in architectural reviews and contribute to long-term platform modernization initiatives.
Collaborate with cross-functional stakeholders including product, security, DevOps, and enterprise architecture teams.

Required Qualifications

5+ years of experience in fullstack software engineering within complex, enterprise environments.
Strong backend development experience using Kotlin.
Proven expertise developing production-grade microservices using Spring Boot.
Hands-on experience with AWS (Amazon Web Services) and cloud-hosted infrastructure.
Experience deploying and managing containerized workloads using Amazon ECS.
Strong frontend development experience with React and modern JavaScript.
Proficiency in TypeScript to enhance scalability, maintainability, and type safety.
Solid understanding of relational database design and advanced SQL (PostgreSQL or MySQL).
Experience with Git-based version control and enterprise development workflows using GitHub.
Strong understanding of object-oriented design principles, design patterns, and distributed systems.
Experience working in regulated or compliance-driven environments is highly preferred.
Excellent communication skills and ability to collaborate across large, matrixed organizations.

Our success over the past 20 years is rooted in our exceptional team, which thrives in a culture of collaboration, creativity, and continuous learning.

We are proud to offer our employees a range of benefits, including competitive compensation, professional development opportunities, and flexible work arrangements, all designed to help them thrive. As we continue to expand, we remain committed to cultivating an environment where people feel valued, have a voice, and are given the tools to grow—both personally and professionally—while pushing the boundaries of innovation in the fintech industry.

Minimum Degree Required:

Bachelor’s Degree, in lieu of a degree, demonstrating in addition to the minimum years of experience required for the role, three years of specialized training and/or progressively responsible work experience in technology for each missing year of college is required