Senior Software Engineer, Backend

Flex is a growth-stage FinTech company headquartered in NYC, focused on creating the best rent payment experience. They are seeking a Senior Engineer to join their backend engineering team, responsible for designing, building, and scaling systems that power core products like Payments and Billing, while collaborating with cross-functional teams to enhance user experience.

Responsibilities:

• 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

Requirements:

• 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