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Senior Staff Software Engineer, Mobile & Web

New York, New York, United States; Remote (U.S.); San Francisco, California, United States

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 2025 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 job

Flex is looking for a Senior Staff Mobile & Web Developer who will be responsible for defining and prioritizing the mobile & web platforms’ technical roadmaps and lead implementation of high-priority, cross-functional strategic initiatives.

In this role, you will work closely with senior product, design and engineering leaders to launch new features for our consumer users.  You will design, develop, test and scale new product offerings that solve complex problems in a simple way for our users.

As a Senior Staff Engineer, you will play a key role in defining solutions for classes of problems, breaking down complex scope into actionable plans, and leading your cross-functional team through implementation.  You will actively improve the level of craftsmanship within the teams you lead by following a high standard for code quality, processes and standards.

Our team works in an agile manner, and favors rapid iterative delivery to deliver value quickly.  We expect you to be hands-on and deliver your own high-impact contributions, while building a solid technical foundation that allows for flexibility as we scale out our product offerings across industry verticals.

What you’ll do

  • You'll lead high priority, cross-functional, and cross-division projects that drive significant impact on the company's direction and growth.
  • You'll advocate for and influence the implementation of architectural best practices that allow our frontend applications to scale for our growing number of users, use cases, and developers contributing to the code base.
  • You’ll work closely with your product, design, and engineering peers to solve our users' most pressing problems.
  • You’ll work directly with engineering leadership to align our technical and product roadmaps, and proactively work with domain owners to help them understand new technical capabilities to build the right roadmap for the business.
  • You’ll be hands-on, make high-impact contributions and roll out changes to our customers in an agile manner with a delivery cadence that favors small, frequent iterations.
  • You'll provide guidance on the long-term vision and architecture of our application stack, ensuring best practices and consistency across the team.
  • You’ll lead by example, mentoring others, and fostering a high-performance culture by improving the level of craftsmanship within the teams you lead. You are responsible for designing and delivering large, complex features/systems that are leveraged across domains.
  • The ideal candidate will be comfortable leading scoping, design, and implementation for product features they build, and can drive their production rollouts to completion with minimum oversight.

Key qualifications

Skills that are required: 

  • Strong computer science fundamentals.
  • Proficiency in React.js/React Native (7+ years) and associated tools (Hooks, Context, Redux).
  • Expertise in designing and delivering large, complex mobile and web UIs that are leveraged across multiple domains.
  • Strong TypeScript development skills, with a focus on maintainability and documentation.
  • Familiar with iOS/Android/web development tool ecosystems (Bonus: Native iOS/Android experience).
  • Strong understanding of REST API design and mobile API best practices.
  • Experience working with distributed services architecture, observability, and monitoring tools (e.g., DataDog).
  • Proven ability to mentor engineers and promote software development best practices, actively improving the level of craftsmanship within the teams you lead.
  • Strong communication skills and experience working with distributed teams.
  • Experience partnering with peers and strategizing with senior leaders across multiple functions within and outside of the company.
  • A high standard for code quality, processes, and standards.

Core competencies:

  • Experience working on cross-functional teams involving product, design, and engineering.
  • Proficient in TypeScript (React.js/React Native) and familiar with Java/Springboot services architecture.
  • Familiar with CI/CD pipelines to improve code stability and quality.
  • Experience with cloud and containerized environments (Bonus: AWS, Kubernetes, MySQL).
  • Comfortable working with IDEs such as VSCode, IntelliJ, XCode, and Android Studio.
  • Motivated to drive team effectiveness and engineering excellence.
  • Ability to apply domain knowledge to solve complex problems with elegant technical solutions that are well integrated with the existing environment.
  • Knowledge and understanding of broader software engineering issues to improve your team's software design.
The salary compensation range for this role will be commensurate with the candidate's experience and Flex's internal leveling guidelines and benchmarks.
  • For working locations in NY/NJ/CA, the base salary pay range will be $247,000-$266,000
  • For all other states, the base salary pay range will be $222,000-$239,000

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.

We offer many employee benefits & perks. For full-time U.S based positions we offer:

  • Competitive medical, dental, and vision available from Day 1
  • Company equity
  • 401(k) plan with company match (our company match kicks off at the beginning of 2026)
  • Unlimited paid time off + 13 company paid holidays
  • Parental leave 
  • Flex Cares Program
  • Free Flex subscription

 For full time non-US employees, we offer

  • Competitive compensation + company equity
  • Unlimited PTO

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