Senior Software Engineer, Backend at Flex

This is a senior role for a backend engineer with a strong foundation in the **Java ecosystem** and experience building distributed systems. The ideal candidate

Work type: remote

Location: Remote (U.S.); San Francisco, California, United States

Salary: $172,000 – $215,000/yr

Type: Full-time

Summary

This is a senior role for a backend engineer with a strong foundation in the **Java ecosystem** and experience building distributed systems. The ideal candidate has 5+ years of experience (at least 4 with Java) and is comfortable owning the entire software lifecycle, from architecture to deployment in AWS environments. Given the fintech focus, experience with high-scale payment processing, risk mitigation, or API design is highly valued. The role offers significant flexibility, with **fully remote** options across the U.S. and a competitive salary reaching up to **$215,000**, plus equity. You’ll have the chance to join one of four specialized teams—Consumer, Core Platform, Partner Integrations, or Risk—allowing for a placement that aligns with your specific technical interests. Benefits are comprehensive, including 401(k) matching and immediate health coverage. **You might be a good fit if you:** * Are a Java expert who is deeply familiar with Spring Boot and the JVM. * Have hands-on experience with modern cloud infrastructure like AWS, Kubernetes, and Terraform. * Enjoy mentoring junior developers and driving technical standards across a growing team. * Thrive in a fast-paced fintech environment where reliability and fault tolerance are critical.

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?

### About the job

Flex is hiring Senior Software Engineer, Backend roles across four engineering teams: Consumer, Partner Integrations, Core Platform, and Risk. When you apply, you will automatically be considered for all open Senior Backend positions, and your placement will be determined based on your experience and expertise assessed during the interview process.

As a Senior Backend Engineer at Flex, you will play a key role in designing, building, and scaling backend services and APIs that power our products, partner integrations, and critical risk management platforms. You’ll collaborate closely with cross-functional teams to deliver robust, fault-tolerant systems that impact renters and partners at scale.

You will own the end-to-end lifecycle of your services- from requirements and architecture through implementation, testing, deployment, and monitoring- and help elevate the team by driving technical best practices and mentoring junior engineers.

Our Engineering Teams

• Consumer Engineering: Builds the APIs and backend systems powering Flex’s main consumer-facing products. This team focuses on delivering scalable services for a seamless rent payment experience through our mobile and web apps.

• Partner Integrations Engineering: Owns the backend services and integrations that connect Flex to financial partners and payment networks, ensuring reliable, secure payment flows and partner-facing experiences.

• Core Platform Engineering: Maintains the backend systems and infrastructure supporting all business features, including Payments, Billing, Identity, and Partner Integrations, ensuring Flex’s foundation is robust and scalable.

• Risk Platform Engineering: Develops the platforms and APIs that mitigate credit and fraud risk, enhancing customer accessibility while safeguarding against misuse through advanced rules engines, machine learning, and event data systems.

### What You'll Do

• Design, develop, test, and scale backend services and APIs that power Flex’s consumer products, partner integrations, risk management systems, and core platform services.

• Build and operate robust, fault-tolerant distributed systems with multiple external dependencies.

• Implement service APIs for web and mobile apps, simplifying complex rent payment processing.

• Work closely with Product, Design, Infrastructure, Sales, Partner, and Customer Success to deliver features and integrations that delight customers and partners.

• Translate feature requirements into technical specifications and lead the architecture and implementation of scalable solutions.

• Drive the full lifecycle of services and APIs you build, including deployment, monitoring, and optimization for high availability and performance.

• Contribute to evolving Flex’s service-oriented architecture, REST APIs, message queues, and scalable systems design.

• Develop risk management systems such as rules engines, ML-powered fraud detection, and high-scale event ingestion pipelines.

• Mentor junior engineers and help elevate the team’s engineering practices through code reviews, architecture discussions, and technical leadership.

• Ensure services are observable and reliable using monitoring tools and industry best practices.

• Collaborate on CI/CD improvements and automation to increase code quality and delivery velocity.

• - Strong computer science fundamentals with a proven track record of building scalable backend systems.

• 5–6+ years of professional software engineering experience with a focus on backend development.

• 4+ years of hands-on Java experience, with deep knowledge of the Java ecosystem.

• Proficient in Java frameworks and tools used at Flex: Spring (core/web/boot), Gradle, JUnit, JVM tuning and performance optimization.

• Experience operating services in distributed, service-oriented architectures at scale.

• Familiarity with REST API design, mobile API best practices, and message-driven architectures.

• Skilled at building robust, fault-tolerant systems and integrating with multiple external dependencies.

• Experience designing and maintaining data pipelines and working with big data platforms (bonus: Snowflake).

• Hands-on experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB), containerization (Docker/Kubernetes), and Infrastructure as Code (CDK/Terraform).

• Skilled in observability and monitoring tools (e.g., DataDog) to ensure high availability.

• Ability to write high-quality code that is testable, maintainable, scalable, and secure, using industry best practices throughout the SDLC (unit testing, build automation, CI/CD).

• Excellent communicator, comfortable working with distributed teams and cross-functional stakeholders.

• Proven ability to mentor junior engineers and raise the technical bar through best practices.

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): $172,000 —$215,000 USD

• Tier B: $154,800—$193,500 USD

• Tier C: $146,200 —$182,750 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

• Competitive compensation + company equity

• Unlimited PTO

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