Senior Software Engineer

Role OverviewFlex is transforming the traditional, fragmented $90B+ moving, storage, and last-mile delivery industry into a seamless, technology-driven experience. We have been building our core operating platform to handle highly complex domain challenges.We're looking for a rock star Senior Full Stack Engineer with a strong backend focus to help build and scale the systems powering Flex's platform. You'll spend most of your time designing APIs, data models, workflows, and services in Node.js — with real ownership over the systems that connect supply, scheduling, and fulfillment — while staying comfortable working across our React, Angular, and React Native codebases.Location & Working HoursThis role is 100% remote within the United States. We optimize for deep work but require consistent daily availability throughout our Core Collaboration Hours (10:00 AM – 4:00 PM EST) for synchronous alignment and cross-functional meetings. Outside of those hours, you are trusted to manage your schedule to maximize high-efficiency and high-quality output.What You’ll DoTranslate architectural and business requirements into actionable technical tasks, owning the delivery of features through to production deployment.Build resilient, well-tested core services using Node.js.Architect MongoDB data models for complex workflows, and continuously optimize performance.Build and maintain integrations with third-party services (payments, mapping/routing, SMS/notifications, CRM, etc.).Contribute to frontend features in React, React Native and Angular whenever work requires full-stack ownership.Participate in technical design reviews and help set backend architecture standards, leveling up the system iteratively.Write clean, maintainable code and include comprehensive testing and CI/CD practices as mandatory components of professional software delivery.Leverage AI tools throughout the development lifecycle — from scaffolding and code generation to debugging and testing — to ship faster with high quality.What We’re Looking For7+ years of professional software engineering experience, with the majority spent on backend systems.Strong experience with Node.js in production.Experience designing and versioning REST or GraphQL APIs consumed by multiple clients.Solid experience with MongoDB — schema design, indexing, aggregation pipelines, and performance tuning at scale.AI-forward mindset — leveraging AI-assisted development tools (e.g., Claude Code, Cursor, Copilot) to accelerate delivery, and enthusiastic about incorporating AI into day-to-day engineering workflows.Comfortable working across the stack — you don’t have to be proficient in all of React, Angular, or React Native, but you should have strong working knowledge in at least one of these and are able to pick up the others.proficient in React and/or React Native for our core product surfaces; our internal admin tooling uses Angular, so familiarity there is a plus but not required.Working familiarity with GCP (Cloud Run, GKE, Pub/Sub, or similar) — enough to understand deployments and debug production issues.Direct experience building or scaling a two-sided marketplace, supply/demand matching engine, or fulfillment platform.Solid instincts for production troubleshooting — reading logs/metrics, isolating root cause, working cross-functionally during incidents.Track record of owning services in production end-to-end.Strong communication skills — able to explain technical tradeoffs to both engineers and non-technical stakeholders.Familiarity with event-driven/queue-based architectures (e.g., Pub/Sub) for coordinating multi-step workflows.Startup/fast-growing company experience where you've had to balance speed with long-term maintainability.