Senior Software Engineer, Backend

Flex; United States; Hybrid; USD 172,000 - 215,000; Full time

Job summary

Flex, a NYC-headquartered fintech, is hiring a Senior Backend Engineer to design, build, and scale services behind Payment, Billing, Identity, and partner integrations. You will own APIs, drive production rollouts, and collaborate with product, design, and engineering to solve rental payments challenges in small iterations.

Join a fast-growing team with high ownership, where you’ll work on fault-tolerant systems, data pipelines, and scalable architectures using Java, Spring, and AWS.

Qualifications

• Minimum 6 years of software engineering experience.
• Minimum 4 years of Java experience.
• Experience working on globally distributed teams with ownership.
• Experience aligning with stakeholders on scope and delivery.
• Ability to thrive in a fast-paced environment.
• Experience building robust, fault-tolerant systems with multiple external dependencies.
• Experience designing, building, and maintaining data pipelines.
• Proficiency with Java frameworks and tools like Spring, Gradle, JUnit, JVM tuning.
• Experience with SOA, REST APIs, message queues, and scalable architectures.
• Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containers.

Responsibilities

• Design, build, and scale services and integrations behind Payment, Billing, Identity, and partner integrations.
• Lead scoping, design, and implementation for APIs you own.
• Drive production rollouts to completion with minimal oversight.
• Collaborate with product, design, and engineering peers to solve renters' problems in small iterations.

Skills

Java

REST APIs

SOA

AWS

CI/CD

Observability

Tools

Spring

Gradle

JUnit

Kubernetes

GitHub Actions

DataDog

Snowflake

CDK

Terraform

Job description

Flex is a growth-stage, NYC headquartered FinTech company that is building the payment layer for life's financial obligations, giving households one place to see, split, and pay their bills around how they live and get paid. By offering greater choice over how and when payments are made and allowing eligible on time payments to help build a positive credit history, Flex puts households back in control of their cash flow.

That work brings together people with different perspectives who challenge the status quo and take ownership of solving difficult problems. For you, that means doing the best work of your career next to people who make you better, and together bringing ideas to life that make a real impact for the people we serve.

About Our Opportunities

Flex exists to make paying rent work the way real life actually works — smoothing out cash flow, helping renters avoid late fees, and letting them build credit instead of falling behind. As a Senior Backend Engineer, you'll design, build, and scale the services and integrations behind Payment, Billing, Identity, and partner integrations that keep rent moving on time for renters every month — leading scoping, design, and implementation for the APIs you own, driving your own production rollouts to completion with minimal oversight, and working closely with product, design, and engineering peers to solve renters' most pressing problems in small, frequent iterations rather than big, risky releases.

About Our Team(s)

We have some really exciting teams who are looking for an amazing engineer like you! Check them out!

• Partner Integrations - Partner integrations work to standardize APIs, tools, and processes that let external partners connect to Flex for data sharing and payments across entry points like Flex Anywhere and Quick-Pay
• Fin Platform - Fin Platform is the monitoring and operations layer for Flex's billing and payment systems, covering dashboards, SLIs/SLOs, runbooks, deployment and on-call procedures to ensure reliability and readiness.
• Money Team - builds and owns the platforms, tooling, and documentation powering Flex's payments, wallet, and settlement finance systems.

Who Thrives Here?

• A Doer — you get things done efficiently, and you're comfortable rolling up your sleeves when something's blocking the team.
• An Owner — you take full accountability for what you build, from design through production, and you always have a plan B.
• Someone Collaborative — you bring people together to pressure-test ideas rather than working in a silo.
• Someone with Precision — your code and your communication are both clear, because ideas only matter once others can act on them.
• Someone Resilient — systems break and priorities shift, and you adapt without losing momentum.
• Someone Humble— you care more about getting to the right answer than being the one who's right.

Qualifications

Minimum Qualifications

• Minimum of 6 years experience in software engineering
• Minimum of 4 years experience with Java
• Ability to work on a globally-distributed team with a high degree of ownership
• Experience working with technical and non-technical stakeholders, successfully aligning and setting expectations on scope and delivery
• Ability to grow in a fast-paced and dynamic environment that will challenge you to always bring your best
• Experience building robust, fault-tolerant systems with multiple external dependencies
• Experience designing, building, and maintaining data pipelines
• Proficient in Java frameworks and tools used at Flex, including Spring (core/web/boot), Gradle, JUnit, and JVM (memory/performance tuning, GC)
• Experience with Service-Oriented Architecture, REST APIs, Message Queues, and scalable architectures
• Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containerization tools

Preferred Qualifications

• Proficient in CI/CD systems (preferably GitHub Actions), git, and automation
• Skilled in observability and monitoring tools, such as DataDog, to ensure high availability
• Experienced with big data platforms and tooling, including Snowflake
• Proficient in Infrastructure as Code, using tools like CDK and Terraform
• Skilled at elevating team standards through best practices, and mentoring junior engineers
• Excellent written and verbal communicator, with experience in cross-functional collaboration

Compensation

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 1 (NYC/Bay Area, Los Angeles, Seattle)

$172,000—$215,000 USD

Tier 2 (Austin, Washington D.C. Philadelphia, San Diego, Chicago, Atlanta)

$154,800—$193,500 USD

Tier 3 (Salt Lake City, all other USA cities)

$146,200—$182,750 USD

Life at Flex

Building a successful company takes a diverse team of intelligent, curious, determined, empathetic, and self-aware people. Our headquarters is in New York City, with employees across the US, Australia, Canada, and South America. We’re growing quickly and deliberately, with a focus on building an inclusive culture. We value the perspectives our people bring and take 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

View our benefits and more at getflex.com/careers.