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Flex · 8 hours ago

Senior Software Engineer, Backend

United States

Full-time

Remote

Mid, Senior Level

$197K/yr - $213K/yr

4+ years exp

Flex is a growth-stage FinTech company headquartered in NYC, focused on improving the rent payment experience. They are seeking a Senior Backend Engineer to design, build, and scale backend services and APIs, collaborating with cross-functional teams to deliver robust systems that enhance the user experience.

AppsBillingFinancial ServicesFinTechSoftware

H1B Sponsor Likely

Responsibilities

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

Qualification

JavaSpring FrameworkAWSDistributed SystemsREST API DesignData PipelinesObservability ToolsMentoringCommunication

Required

A minimum of 4 years of experience with Java is required for this position

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

Preferred

Experience in risk engineering, rules engine architecture, and implementing risk/fraud/credit policies in production systems is highly valued

Benefits

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

Competitive compensation + company equity

Unlimited PTO

Company

Flex

Glassdoor3.9

Flex enables people to pay rent bills on a schedule that fits their personal finances.

Founded in 2019

New York, New York, USA

201-500 employees

https://getflex.com

H1B Sponsorship

Flex has a track record of offering H1B sponsorships. Please note that this does not guarantee sponsorship for this specific role. Below presents additional info for your reference. (Data Powered by US Department of Labor)

Distribution of Different Job Fields Receiving Sponsorship

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Trends of Total Sponsorships

2025 (1)

2024 (1)