Staff Software Engineer, Partner Integrations
WFA Digital Insight
Flex’s mission to make rent payments flexible translates into a technically demanding platform where payments must move reliably across banks and partners. The Staff Software Engineer for Partner Integrations sits at the crossroads of API design, SDK development, and embedded web experiences, directly influencing how renters interact with Flex’s product. Unlike a generic backend role, this position requires ownership of the entire integration lifecycle—from architecture decisions on AWS services to hands‑on coding in Java/Spring and ensuring observability at scale. Candidates will collaborate with product, design, sales and customer‑success teams, meaning technical solutions must align with real‑world partner requirements. Success in this role means balancing rapid delivery with the rigor needed for financial transactions, while mentoring a growing engineering crew.
Job Description
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? As we continue to grow our talented team, we remain committed to radical transparency, integrity, and individual growth. We believe that your unique background and experience adds tremendous value to the organization and will empower you to take absolute ownership of business challenges and the execution of solutions. What we need: Flex is looking for a Staff Software Engineer to join our Partner Engineering organization and help build out our payment integrations platform & user experiences. You will help shape the technical roadmap for the team, working across APIs, SDKs, and Web experiences. You will work with teams across the organization including Engineering, Product, Design, Infrastructure, Sales, Partner and Customer Success to deliver products that wow our customers and drive business goals. We expect you to be hands-on and execute work as an individual, and build products that allow for flexibility as we evolve our product offerings. What you'll do Design, implement, and maintain our payment integrations platform, including partner APIs, SDKs, and embedded web experiences Help shape and drive the technical roadmap for the Partner Engineering team Design and develop scalable APIs and integrations to support money movements across our banking partners via payment rails such as ACH Work cross-functionally with Engineering, Product, Design, Infrastructure, Sales, Partner, and Customer Success to deliver high-impact features Scale our integrations platform to support business growth while maintaining performance and reliability Continuously improve daily operations through automation, tooling, design evolution, and observability Mentor engineers and elevate team standards through best practices, code reviews, and technical guidance What We’re Looking For: Minimum 8 years of experience in software engineering Minimum 4 years of experience with Java; proficient in Spring (core/web/boot), Gradle, JUnit, and JVM tuning Experience with Service-Oriented Architecture, REST APIs, message queues, and scalable distributed systems Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containerization Experience leading delivery of multiple high-impact products end to end, on time with a high quality bar Ability to work on a globally-distributed team with a high degree of ownership Experience aligning technical and non-technical stakeholders on scope and delivery Experience in FinTech and familiarity with major payment rails Ability to drive quality and consistency across your team without compromising velocity
Nice to Have
Proficient in CI/CD systems (preferably GitHub Actions) and automation Skilled in observability and monitoring tools such as DataDog Experienced with big data platforms including Snowflake Proficient in Infrastructure as Code (CDK, Terraform) Excellent written and verbal communicator with cross-functional collaboration experience Compensation Flex takes a market-based approach to pay, and compensation may vary depending on your primary work location. Work locations are categorized into one of three tiers based on a cost of labor index for that geographic area. The successful candidate’s starting pay will be commensurate with their experience, qualifications, and Flex’s internal leveling guidelines and benchmarks. Tier 1 (NYC/Bay Area, Los Angeles, Seattle) $200,000 — $250,000 USD Tier 2 (Austin, Washington D.C. Philadelphia, San Diego, Chicago, Atlanta) $180,000 — $225,000 USD Tier 3 (Salt Lake City, all other USA cities) $170,000 — $212,500 USD 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 PTOHow to Stand Out
- Highlight concrete examples of Java/Spring projects you’ve led, especially those involving payment APIs or financial data.
- Prepare a short architecture diagram of a past integration system to discuss design decisions and trade‑offs.
- Demonstrate familiarity with AWS services mentioned (EKS, Aurora, DynamoDB) by describing how you’ve used them in production.
- Emphasize collaboration experience; be ready to share stories of working with product, design or sales teams to ship features.
- Bring metrics on system reliability or performance improvements you achieved – quantifiable impact resonates strongly.
- Review Flex’s core product (flexible rent payments) so you can speak to how your work would directly support their mission.
- Ask about on‑call expectations and the team’s observability stack to show proactive interest in operational excellence.
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