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 Role

Flex is hiring a Senior Engineer to join our backend engineering team, where you'll be responsible for designing, building, and scaling the systems that power our core products — including Payments, Billing, Identity, and partner integrations. You'll work on services that directly shape how hundreds of thousands of renters experience financial flexibility, and your work will have a measurable impact on the reliability and performance of everything we ship.

In this role, you'll own meaningful portions of our backend infrastructure end-to-end — from scoping and API design through production rollout — with the autonomy to make independent technical decisions that drive real customer and business impact. You'll collaborate closely with product, design, and engineering peers in an agile environment that favors small, frequent iterations over big-bang releases. The ideal candidate is comfortable leading without being asked and takes pride in shipping high-quality, fault-tolerant systems.

At Flex, engineers are expected to bring both technical depth and a builder's mindset. You'll be working within a globally distributed team, partnering with technical and non-technical stakeholders alike, and contributing to a codebase that scales with an ambitious product roadmap. If you thrive in fast-moving environments and want your engineering work to directly improve how people pay rent, this role is for you.

What You'll Do

Own multiple backend team goals and projects, delivering on time and with high quality with minimal oversight
Design, build, and scale backend services and APIs across core domains including Payments, Billing, Identity, and partner integrations
Make independent technical decisions that maximize customer and business impact, balancing speed with long-term system health
Write elegant, well-tested code and provide constructive, thorough code reviews that elevate team standards
Lead scoping and design discussions for new features and systems, driving production rollouts to completion
Integrate AI-assisted development tools into your daily workflow as a default, and mentor teammates on responsible and effective AI usage
Partner with product, design, and cross-functional engineering peers to solve high-priority user problems around rent payment
Contribute to observability, reliability, and performance standards across the services you own

What You'll Bring

6+ years of software engineering experience, with at least 4 years of hands-on Java development
Proficiency in Java frameworks and tooling including Spring (core/web/boot), Gradle, JUnit, and JVM tuning (memory, performance, GC)
Experience designing and building robust, fault-tolerant systems with multiple external dependencies using Service-Oriented Architecture, REST APIs, and message queues
Hands-on experience with AWS services (EKS, Aurora RDS, ElastiCache, DynamoDB) and containerization tooling
Comfort working on a globally distributed team with a high degree of ownership and strong stakeholder communication skills
Experience with CI/CD systems (preferably GitHub Actions), git, and automation practices
Familiarity with observability and monitoring tools such as Datadog to maintain high availability
Consistent use of AI-assisted development tools (code generation, test writing, documentation) with full ownership of correctness, security, and quality

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