Senior Software Engineer, Mobile & Web Remote; U.S

Senior Staff Software Engineer, Mobile & Web

Flex is a growth-stage, NYC headquartered Fin Tech 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?

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.

• 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.

• 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 Type Script 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., Data Dog).
• Proven ability to mentor engineers and promote software development best practices, actively improving the level of…