Staff Software Engineer, Partner Integrations

flex

Remote

Posted Jun 9, 2026

Full-time
Hybrid
Biller Engineering

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 PTO