Senior Software Engineer, Mobile & Web

Senior Software Engineer, Mobile & Web at Flex

Flex is a growth-stage, NYC headquartered FinTech company that is creating the best rent payment experience. We empower renters with flexibility over their most significant recurring expense by enabling them to pay rent throughout the month on a schedule that better fits their finances and budget. After deliberately keeping a stealth profile, we are now looking for motivated individuals to help us keep our mission growing.

About The Job

Flex is seeking a Senior Software Engineer, Mobile & Web to lead the development of our core user experience across both mobile and web platforms. In this dynamic role, you will be an integral part of an agile team, responsible for launching new features, designing, testing, and scaling innovative product offerings that simplify complex problems for our diverse user base.

Responsibilities

• Develop, design, test, and scale new product offerings across web and mobile platforms.
• Work closely with cross-functional partners including designers, product managers, and quality engineers.
• Be hands-on, executing individual tasks while building flexible products that evolve with our offerings.
• Ensure the delivery of high-quality mobile and web UIs that meet precise specifications.
• Lead and deliver products for large-scale user bases (hundreds of thousands to millions) without performance bottlenecks.
• Write maintainable, well-documented, and testable TypeScript code using industry best practices for the entire software development lifecycle.
• Collaborate with engineers across multiple teams to continuously improve code quality.
• Mentor other engineers in best practices for software development.

Minimum Qualifications

• Strong computer science fundamentals.
• A minimum of 4 years of experience in React.js or React Native.
• Strong focus on building high-quality mobile and web UIs to specifications.
• Experience with various architectures and tools within the React Native and React ecosystems (Hooks, Components, Context, Redux).
• Experience leading and delivering products at a large scale without performance bottlenecks (hundreds of thousands to millions of users).
• Ability to write maintainable code that uses industry best practices to improve the entire software development lifecycle (unit testing, linting, automation).
• Ability to write well-documented and testable TypeScript code.
• Familiarity with REST APIs and tooling across web and mobile architectures.
• Ability to collaborate with engineers across multiple teams to improve code quality.
• Able to mentor engineers in using best practices for software development.

Preferred Qualifications

• Prior experience working on cross-functional teams.
• Proficient with TypeScript (Bonus: Native iOS/Android).
• Experience with CI/CD to improve code stability and code quality.
• Experience with IDEs such as VSCode & Android Studio & XCode.
• Familiar with Android / iOS / Web development tool ecosystem.
• Motivated to help other engineers succeed and be effective.

Compensation & Benefits

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 believe a diverse team of intelligent, curious, determined, empathetic, and self-aware individuals is key to growing a successful company. While our HQ is in New York City, our employees are located throughout the US, Australia, Canada, and South America. We are rapidly and deliberately growing, focusing on building an inclusive culture. We are an equal opportunity workplace, valuing the incredible perspectives our dynamic team brings, and we know you do too.

Employee Benefits & Perks (U.S. Full-time)

• Competitive medical, dental, and vision available from Day 1.
• Company equity.
• 401(k) plan with 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.

Employee Benefits (Non-U.S. Full-time)

• Competitive compensation + company equity.
• Unlimited PTO.

Key skills/competency

• React.js
• React Native
• TypeScript
• UI Development
• Mobile Development
• Web Development
• REST APIs
• Agile Methodology
• Software Engineering
• Performance Scaling