Software Engineer II, Backend

Flex is a growth-stage FinTech company headquartered in NYC, focused on creating a better rent payment experience. They are seeking a Backend Engineer to design, build, test, and scale backend services and APIs that power their consumer products and partner integrations.

Responsibilities:

• Design, develop, test, and scale backend services and APIs that power Flex’s products, partner experiences, and internal platforms
• Implement the service APIs used by our mobile and web apps to simplify complex rent payment processing
• Build robust, fault-tolerant systems that integrate with multiple external dependencies and ensure high reliability
• Work closely with cross-functional teams—including Engineering, Product, Design, Infrastructure, Sales, Partner, and Customer Success—to deliver features and integrations that wow both customers and partners
• Translate feature requirements into well-structured technical specifications and scalable solutions
• Lead scoping, design, and implementation for the APIs you build and drive production rollouts with minimal oversight
• Contribute to service-oriented architecture, scalable system design, and internal best practices for distributed services environments
• Collaborate with peers to evolve Flex’s technical architecture as the company and product offerings grow
• Ensure services are observable and highly available through effective use of monitoring tools and practices
• Participate in code reviews, CI/CD improvements, and efforts to increase code quality and stability

Requirements:

• Strong computer science fundamentals and passion for building scalable backend systems
• 2–3+ years of professional software engineering experience with a focus on backend services
• Proficient in Java with hands-on experience using Flex's core stack: Spring (core/web/boot), Gradle, JUnit
• Experience building and maintaining distributed services and APIs at scale in production environments
• Familiar with REST API design, mobile API best practices, and service-oriented architectures
• Experience building fault-tolerant systems with multiple external dependencies
• Skilled in observability and monitoring tools (e.g., DataDog) to ensure high availability
• Ability to write high-quality code that is testable, maintainable, scalable, and secure
• Demonstrated ability to translate business requirements into technical specifications and deliver high-impact solutions
• Excellent communicator who thrives in a collaborative, globally-distributed team environment
• Comfortable working with both technical and non-technical stakeholders and setting expectations on scope and delivery