Senior Software Engineer, Risk Platform & ML Rules

Flex is a growth-stage, NYC headquartered FinTech company that is creating the best rent payment experience. It’s hard to believe that it’s 2026 and paying rent on time is expensive, inflexible, and difficult. We’re here to change that! Flex enables our users to pay rent throughout the month on a schedule that better fits their finances and budget. Our mission is to empower as many renters as possible with flexibility over their most significant recurring expense. After deliberately keeping a stealth profile as we built up unprecedented investor support and an enthusiastic user base, we are looking for motivated individuals to help us keep our mission growing. Will you be a part of the team? About the role Flex is looking for a Senior Software Engineer to join our Risk Platform team. This role involves spearheading the implementation of platforms and APIs crucial for supporting business features within the risk management domain. The Risk Platform team is dedicated to mitigating both credit risk and fraud risk. Our mission is to enhance Flex app accessibility for customers while safeguarding against improper use and unauthorized access by identifying and preventing misuse across all core product areas. Following are some projects/systems in Risk Platform you will have opportunities to work with: Core rules engine which is an end-to-end solution for the enterprise decision management lifecycle, including business rule management, analytics, process management, and ML/AI. Event data stream ingestion which supports near real-time fraud rules setup. Advanced a/b testing and experimentation capabilities for our customers so they can leverage greedy algorithms and fight fraud. What you’ll do Build rules engine / machine learning solutions to respond to/mitigate business risks in Flex. Design and develop 24/7 high-scale APIs and distributed systems. The tech stack will be on AWS. Java would be the language for the existing code base. Java Spring Boot will be the framework. Work closely with product, design, and engineering peers to launch new features across our web and mobile platforms Qualifications Minimum Qualifications Must-have : Experience working in a risk engineering team, specializing in rules engine architecture or risk/credit/fraud systems. Must-have : Experience implementing risk policies in a rules engine or production services. 6+ years of professional software development experience. 5+ years of hands-on Java experience. Proficient in Java frameworks and tools used at Flex, including Spring (core/web/boot), Gradle, JUnit, and JVM (memory/performance tuning, GC). Experience with Service-Oriented Architecture, REST APIs, Message Queues, and scalable architectures. Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containerization tools. Preferred Qualifications Proficient in CI/CD systems (preferably GitHub Actions), git, and automation. Skilled in observability and monitoring tools, such as DataDog, to ensure high availability. Experienced with big data platforms and tooling, including Snowflake. Proficient in Infrastructure as Code, using tools like CDK and Terraform. Skilled at elevating team standards through best practices, and mentoring junior engineers. Excellent written and verbal communicator, with experience in cross-functional collaboration. Tier A (NYC/SF): $172,000—$215,000 USD Tier B: $154,800—$193,500 USD Tier C: $146,200—$182,750 USD #LI-Remote Life at Flex We understand that it takes a diverse team of highly intelligent, curious, determined, empathetic, and self aware people to grow a successful company. Our HQ is located in New York City, but we have employees located throughout the US, Australia, Canada and South America. We are growing quickly, but deliberately, with a focus on building an inclusive culture. Our dynamic team has incredible perspectives to share, just as we know you do, and we take great pride in being an equal opportunity workplace. Offices Roles posted in New York, San Francisco, and Salt Lake City are hybrid positions with on-site expectations of 2-3 days per week in our local offices. For candidates outside of these areas, you may be eligible for our relocation assistance program. Benefits For full-time U.S. employees we offer: Competitive medical, dental, and vision Company equity 401(k) plan with company match Unlimited paid time off + 13 company paid holidays Parental leave Free Flex subscription For full-time non-U.S. employees, we offer: Competitive compensation + company equity Unlimited PTO #J-18808-Ljbffr FLEX Inc