Staff Software Engineer, Backend, Money Team

Flex

3d•$170,000 - $250,000•Hybrid

About The Position

Flex is a growth-stage, NYC headquartered FinTech company that is creating the best rent payment experience. We are seeking a Staff Software Engineer to join our Money Team, responsible for building and scaling the financial infrastructure that powers payments, billing, subscriptions, payouts, ledgers, and other money movement systems across the company. As a Staff Engineer, you will provide technical leadership across multiple teams, drive the architecture of mission-critical financial platforms, and help ensure our systems are secure, reliable, compliant, and scalable. You will partner closely with Product, Finance, Risk, Compliance, Data, and Engineering teams to deliver high-impact solutions that directly affect revenue, customer experience, and business operations.

Requirements

6–8+ years of professional software engineering experience, with a focus on backend development.
4+ years of hands-on Java experience (Spring core/web/boot, Gradle, JUnit, JVM tuning & performance).
Strong computer science fundamentals and proven experience designing scalable, distributed systems.
Deep experience building or operating financial systems, including payments, money movement, ledgers, settlements, reconciliation, billing, or banking infrastructure.
Experience integrating with payment processors, settlement, card networks, banking partners.
Strong understanding of transactional systems, financial data consistency, idempotency, auditability, and fault tolerance in distributed environments.
Skilled at working with both technical and non-technical stakeholders, aligning on scope and delivery.
Ability to write high-quality, testable, maintainable, and secure code.
Hands-on experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB), containerization (Docker/Kubernetes), and relational + NoSQL databases (MySQL, PostgreSQL, DynamoDB).
Proficient with CI/CD pipelines (GitHub Actions preferred), git, and build automation.
Familiar with observability and monitoring tools (e.g., DataDog) for maintaining service availability.
Excellent communicator, comfortable collaborating in globally distributed teams.
Track record of mentoring engineers and raising team standards through best practices.

Responsibilities

Design, build, and scale backend services and APIs that power Flex's core financial infrastructure, including payments, money movement, billing, settlements, reconciliation, and ledger systems.
Lead the architecture and evolution of highly available, fault-tolerant financial platforms that process and track millions of dollars in transactions with accuracy, reliability, and auditability.
Provide technical leadership and guidance on distributed systems design, financial data consistency, transaction integrity, and long-term platform strategy.
Drive the delivery of highly impactful initiatives end-to-end, from requirements gathering and technical design through implementation, rollout, and operational excellence.
Partner closely with Product, Finance, Risk, Compliance, Operations, and cross-functional engineering teams to deliver scalable and compliant payment experiences.
Build robust systems that integrate with external payment processors, banking partners, card networks, and financial service providers.
Design and implement resilient ledger, settlement, and reconciliation workflows that ensure financial accuracy across the ecosystem.
Drive adoption of engineering best practices across the organization, including observability, automated testing, reliability engineering, CI/CD, and secure software development.
Mentor and support engineers on the team, raising the technical bar and fostering a culture of technical excellence and ownership.
Operate mission-critical financial services in production with stringent uptime, security, compliance, and performance requirements.
Contribute to the evolution of Flex's service-oriented architecture, event-driven systems, APIs, message queues, and scalable financial platforms.
Balance hands-on execution with architectural leadership, ensuring both rapid delivery and long-term maintainability of critical money movement systems.