Senior Software Engineer, Fullstack

Posted Yesterday
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Hiring Remotely in San Francisco, CA, USA
In-Office or Remote
146K-210K Annually
Senior level
Fintech • Payments • Real Estate • Software • Financial Services
Flex splits your rent, and rent-associated costs, into smaller, stress-free payments throughout the month.
The Role
As a Senior Software Engineer, you will develop and scale user and partner experiences, build APIs, and optimize the onboarding process.
Summary Generated by Built In

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?

Flex is looking for an Engineer to join our dynamic team and play a pivotal role in accelerating our growth trajectory. In this role, you will be instrumental in developing and scaling the platform and app experiences that empower our users and partners, unlocking our next phase of 10x growth.

What You'll Do:

  • Focus on creating exceptional user and partner experiences that drive engagement and retention.
  • Partner closely with product managers, designers, and data scientists, data analysts to identify and solve critical user onboarding challenges.
  • Design, develop, test, and deploy robust APIs, services and data pipelines that enhance user onboarding and overall platform experience.
  • Implement changes through an agile methodology, prioritizing rapid iteration and continuous improvement.
  • Utilize data and analytics to measure the impact of your work and identify opportunities for optimization.
QualificationsMinimum Qualifications
  • 5+ years of professional software development experience.
  • 3+ years of hands-on experience with Java.
  • 3+ years of experience with React or React Native.
  • 3+ years of experience with TypeScript.
  • Having experience building high-quality mobile and web UIs to specifications is a must to have.
  • 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 architectures and tools in React Native and React ecosystems (Hooks, Components, Context, Redux).
  • Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containerization tools.

Preferred Qualifications

  • Have the experience to build and improve user onboarding funnel and design the comprehensive experiment to drive metric improvements.
  • 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.
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 A (NYC/SF/Seattle): $172,000—$210,000 USD
  • Tier B: $154,000—$190,000 USD
  • Tier C: $146,000—$180,000 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 
  • Flex Cares Program: Non-profit company match + pet adoption coverage
  • Free Flex subscription

 For full-time non-U.S. employees, we offer:

  • Competitive compensation + company equity
  • Unlimited PTO

Skills Required

  • 5+ years of professional software development experience
  • 3+ years of hands-on experience with Java
  • 3+ years of experience with React or React Native
  • 3+ years of experience with TypeScript
  • Experience building high-quality mobile and web UIs
  • Proficient in Java frameworks including Spring, Gradle, JUnit
  • Experience with Service-Oriented Architecture, REST APIs
  • Experience with AWS and containerization tools

Flex Compensation & Benefits Highlights

The following summarizes recurring compensation and benefits themes identified from responses generated by popular LLMs to common candidate questions about Flex and has not been reviewed or approved by Flex.

  • Healthcare Strength Day-1 medical, dental, and vision coverage is explicitly offered and framed as “best-in-class coverage and options,” suggesting strong baseline health benefits. Additional listings also describe broad health-support elements such as IVF/adoption and gender transition benefits, reinforcing depth in healthcare-related coverage.
  • Retirement Support A 401(k) is available, with a stated company match starting in early 2026, indicating improving retirement support. This rollout appears to address earlier gaps where matching was not consistently present.
  • Leave & Time Off Breadth Unlimited PTO plus company holidays (and, in some descriptions, shutdown days) indicates a wide time-off policy on paper. Hybrid work flexibility and office-day meal credits can add to the overall rewards value for NYC-based employees.

Flex Insights

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The Company
HQ: New York, NY
419 Employees
Year Founded: 2019

What We Do

Flex, an NYC-headquartered FinTech company, has created a trusted rent payment experience. It’s hard to believe that it’s 2024 and paying rent on time is expensive, inflexible, and difficult; we’re here to change that! We enable our users to pay rent throughout the month on a schedule that better fits their finances and budget, while also helping them build credit. Our mission is to empower as many renters as possible with flexibility over their most significant recurring expense.

Why Work With Us

We believe it takes a diverse team of curious, determined, empathetic, and self aware people to grow a successful company. We value the unique and dynamic perspectives our team brings to solve critical problems that impact the lives of our users and the financial decisions they make.

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