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Salary: USD 200,000 - 250,000 / annual
Flex is a growth-stage fintech company headquartered in NYC that is transforming rent payments by enabling users to pay throughout the month on a flexible schedule. The company is seeking a Staff Software Engineer to join the MarTech (Marketing Technology) team, which serves as the connective layer between ad platforms, website, messaging systems, analytics, and product data.
The MarTech team owns growth engineering end-to-end across Lifecycle Marketing (email & SMS), Performance Marketing (paid acquisition), Brand (social and web properties), and Product Marketing. The team turns marketing spend into a measurable, repeatable growth engine and enables marketing to launch, test, and personalize campaigns without requiring hand-built engineering for each initiative.
Key projects and systems include: an incentive platform for event-driven credit assignment (referrals, affiliates, campaigns); attribution and measurement systems (conversion APIs, identity resolution, spend/event pipelines); customer-facing web experiences (getflex.com and paid-acquisition landing pages); and lifecycle messaging (campaign orchestration, audience syncs, event-driven notifications).
Responsibilities:
- Build and own full-stack marketing services and web experiences that drive customer acquisition and retention
- Design and develop 24/7 high-scale APIs, event-driven services, and data pipelines on AWS (Java/Spring Boot backend; TypeScript/React frontend)
- Build measurement into everything shipped; integrate third-party ad, analytics, and messaging platforms behind durable abstractions
- Work closely with marketing, data, product, design, and engineering peers to launch features and experiments across web and mobile
Requirements:
Minimum Qualifications:
- 8+ years of professional software development experience
- 6+ years of hands-on experience with Java
- 3+ years of experience with TypeScript
- 3+ years of experience with React (or React Native), including modern architectures and tooling (Hooks, Components, Context, state management)
- Excellent written and verbal communication skills with experience in cross-functional collaboration, especially translating between marketing goals and engineering tradeoffs
- Proven experience building high-quality, high-performance web and mobile UIs to spec, including responsive, SEO-conscious, conversion-optimized pages
- Proficiency in Java frameworks and tools (Spring core/web/boot, Gradle, JUnit, JVM memory/performance tuning, GC)
- Experience with service-oriented architecture, REST APIs, webhooks, message queues, event-driven design, and scalable architectures
- Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containerization tools
- Comfort integrating and debugging third-party APIs and SDKs with rate limits, partial failures, and reconciliation
Preferred Qualifications:
- Experience on a growth, marketing engineering, or MarTech team
- Hands-on experience with platforms such as Braze, Singular/AppsFlyer/Branch, Google Tag Manager, Amplitude, LaunchDarkly, or Meta/Google/TikTok/Apple ad and conversion APIs
- Familiarity with attribution, identity resolution, conversion tracking, and privacy constraints (consent management, state privacy laws, platform tracking restrictions)
- Experience with A/B testing, experimentation frameworks, web performance optimization, and headless/CMS content tooling
- Experience with big data platforms including Snowflake
- Proficiency in CI/CD systems (preferably GitHub Actions), git, automation, observability tools (DataDog), and Infrastructure as Code (CDK or Terraform)
- Skilled at elevating team standards through best practices and mentoring junior engineers
