Senior Backend Engineer - US

About Kintsugi Kintsugi is solving sales tax compliance for founders, finance, and accounting teams scaling across multiple states and countries. Our mission is to eliminate the complexities of sales tax through automation, AI, and deep integrations with leading billing, commerce, and accounting platforms. Backed by top investors, Kintsugi is scaling fast, and we’re looking for a Senior Backend Engineer to help us build a world-class tax automation platform. Role Overview As a Senior Backend Engineer at Kintsugi, you will be a key contributor to our core infrastructure and backend services. You will work on designing, developing, and optimizing our APIs, data processing systems, and integrations with third-party platforms. This is a high-impact role for an experienced engineer who thrives in fast-paced environments, takes ownership, and enjoys solving complex technical challenges. Responsibilities Backend Development & Architecture Design and build scalable, high-performance backend services and APIs. Develop and maintain robust, fault-tolerant data processing pipelines. Ensure the security, reliability, and performance of our backend infrastructure. Optimize database schemas and queries for efficiency and scalability. Write clean, maintainable, and well-documented code that follows industry best practices. Systems Integration & Scalability Develop and maintain integrations with third-party billing, commerce, and accounting platforms. Work with serverless technologies and event-driven architectures to build scalable solutions. Ensure smooth data synchronization across multiple systems and platforms. Technical Leadership & Collaboration Participate in architectural decisions and drive technical direction. Conduct code reviews and provide mentorship to junior engineers. Collaborate cross-functionally with Product, Engineering, and Customer Success teams to align technical development with business needs. Testing, Monitoring & Deployment Implement and maintain comprehensive automated testing for backend services. Set up monitoring, logging, and alerting to ensure system health and performance. Deploy and manage services using CI/CD pipelines and Infrastructure-as-Code (IaC) practices. Qualifications 6+ years of experience in backend development with modern programming languages (Python, Node.js, or similar). Expertise in designing and building RESTful and event-driven APIs with Flask Strong experience with relational databases (Postgres, MySQL) and data modeling. Experience working with AWS services (Lambda, S3, DynamoDB, API Gateway, etc.) and serverless architectures. Solid understanding of distributed systems, caching, and performance optimization. Experience working with authentication, authorization, and security best practices. Proficiency in writing automated tests and working in test-driven development environments. Strong problem-solving skills and ability to work independently in a fast-paced startup environment. Experience with SaaS, fintech, or tax technology is a plus but not required. Why Join Us? Build mission-critical backend systems at a rapidly growing, high-impact startup. Work with cutting-edge technologies and solve challenging technical problems. Competitive compensation, meaningful equity, and a fast-paced, high-ownership culture. Opportunity to shape the technical direction and make a significant impact on the company’s success.