Senior Full-Stack Software Engineer

Our client is seeking a Senior Full-Stack Software Engineer (Backend-Leaning) with 8–12 years of experience to bring strong architectural thinking, engineering maturity, and product ownership to the team.This role goes beyond writing code in isolation—it focuses on making sound technical decisions and driving system design. You will operate as a principal-level individual contributor, shaping how systems are designed and built while remaining hands-on across the stack.The ideal candidate has experience working in Series A/B startup environments, understands how to scale real-world products, and can bring a pragmatic, high-quality engineering mindset to a fast-paced, technically complex team.Key ResponsibilitiesOwn system architecture across the stackDrive high-quality architectural decisions across backend, frontend, APIs, data models, and infrastructure, with a focus on simplicity, reliability, and scalability.Build and deliver end-to-end product featuresDesign, develop, and deploy complex features across Python backend systems and React/TypeScript frontend applications, ensuring production-grade quality.Develop data-intensive systemsBuild and optimize systems handling large-scale data ingestion, streaming, and processing, particularly from hardware and edge devices.Enable real-time, multi-user experiencesDesign and implement systems that support collaborative, real-time interactions across users and environments.Lead through technical excellenceAct as a principal-level engineer by guiding architectural direction, setting engineering standards, and mentoring a technically strong but less experienced team.Translate ambiguity into scalable systemsPartner closely with founders to convert ambiguous product ideas into simple, reliable, and scalable solutions.Required Qualifications8–12 years of experience in full-stack software engineering, with a strong focus on Python and React/TypeScriptExperience building complex, production-grade systems, involving either: Multi-user / real-time collaboration platforms (e.g., Figma-like systems), or Computation-heavy platformsProven experience owning or influencing system architecture across backend, APIs, data models, infrastructure, and/or frontendExperience making architectural decisions for production systems used by real usersStrong technical leadership skills with the ability to guide architectural designMust Have SkillsExperience working at a Series A or B startup (joined early and scaled with the company)Hands-on experience as a true full-stack developer (Python + React)Ability to work in-office 4 days per week in NYCNice to HaveExperience designing or scaling data streaming or ingestion pipelines (real-time or large-scale preferred)Experience with event-driven or distributed systems