Senior Fullstack Engineer

Posted 12 Hours Ago
3 Locations
In-Office or Remote
Senior level
Artificial Intelligence • eCommerce • Retail • Software
The Role
Build reusable client-side JavaScript/CSS SDKs and multi-tenant frontend architecture. Develop high-performance React/Next.js applications with Tailwind CSS, implement SSR/SSG/ISR, integrate with REST/GraphQL backends, optimize performance, and support backend data modeling, cloud deployment (AWS/GCP), CI/CD, and production monitoring.
Summary Generated by Built In

About SpangleAI

Launched in 2025, Spangle AI is the agentic conversion layer connecting AI-led discovery to real-time conversion. We've partnered with enterprise brands like REVOLVE, Alexander Wang, and Steve Madden, delivering up to 50% conversion lifts and 2x ROAS improvements.

We recently closed a $15M Series A. Spangle won NRF’s VIP (Vendor in Partnership) Award for Best AI-Driven Marketing Solution and was recognized in Business of Fashion’s AI startups to Watch. 

Founded by serial entrepreneurs with 30+ years scaling AI and commerce at Amazon, Saks, and Gap, we're building the commerce infrastructure for the agentic era, where ChatGPT Shopping, Google AI Overviews, and Meta are reshaping how consumers discover and buy.

The Role

We are seeking exceptional Senior Fullstack Engineers with deep expertise in client-side development to build our next-generation merchant experience platform.This role primarily focuses on: Client-side SDK development, Multi-tenant architecture, Enterprise integration frameworks and High-performance frontend systems.

You will also contribute strategically to backend systems, including data modeling, infrastructure

planning, and scalable deployment architecture.


This role is ideally based in Seattle, the Bay Area, or Austin, with flexibility for exceptional

candidates.

What you'll own:

  • Client-Side Platform & SDK Development: Design and implement reusable, distributed JavaScript/CSS SDK frameworks that enable seamless merchant integration across diverse retail environments. Build scalable multi-tenant frontend architecture that supports enterprise-grade customization and performance.
  • Frontend Engineering: Develop high-performance, scalable, and accessible web applications using React, Next.js, and Tailwind CSS. Implement modern rendering strategies (SSR, SSG, ISR) to ensure optimal SEO and performance.
  • API & Backend Integration: Partner with backend engineers to integrate frontend logic with RESTful APIs and GraphQL services. Ensure secure, resilient communication between client-side SDKs and backend systems.
  • Performance & Scalability Optimization: Drive performance improvements through code splitting, lazy loading, image optimization, caching strategies, and runtime efficiency tuning.
  • Code Quality & Standards: Write clean, maintainable, and reusable code. Enforce best practices for accessibility (a11y), SEO, modular architecture, and automated testing.
  • Backend & Infrastructure Support: Contribute to data modeling, database schema design, infrastructure planning, and cloud deployment (AWS/GCP). Support CI/CD processes and production monitoring.

What We're Looking For

Experience

  • 5+ years of professional software development experience
  • Proven experience building production-grade web applications in multi-tenant or enterprise environments
  • Experience developing distributed client-side SDKs or embedded commerce tools is strongly preferred

Technical Skills

  • Expert-level proficiency in JavaScript, TypeScript, and CSS
  • Deep expertise in React, Next.js, and Tailwind CSS
  • Proficient with the AI native coding tools such as cursor, codex and claude code
  • Strong understanding of multi-tenant build systems and distributed JavaScript/CSS framework design.
  • Experience with RESTful APIs and/or GraphQL integrations.
  • Solid understanding of data modeling, database schema design, and backend architecture principles
  • Familiarity with cloud infrastructure (AWS or GCP) and modern DevOps practices
  • Strong understanding of frontend performance optimization and rendering strategies

Our Culture

  • GenAI-native in how we build, sell, and operate
  • High ownership, low overhead, and bias toward action
  • Focus on speed, experimentation, and execution
  • Deep emphasis on creating clear, demonstrable customer value
  • Preference for builders and operators over hierarchy
  • Strong belief in in-person collaboration

Why Spangle

  • Opportunity to build foundational platform technology at a fast-growing AI startup
  • Direct impact on product architecture and technical direction
  • Competitive salary with uncapped commission and equity
  • Benefits: Health, dental, and vision insurance, 401(k), Unlimited PTO

Skills Required

  • 5+ years of professional software development experience
  • Proven experience building production-grade web applications in multi-tenant or enterprise environments
  • Experience developing distributed client-side SDKs or embedded commerce tools
  • Expert-level proficiency in JavaScript, TypeScript, and CSS
  • Deep expertise in React, Next.js, and Tailwind CSS
  • Proficiency with AI-native coding tools such as Cursor, Codex, and Claude Code
  • Experience with RESTful APIs and/or GraphQL integrations
  • Strong understanding of multi-tenant build systems and distributed JavaScript/CSS framework design
  • Solid understanding of data modeling, database schema design, and backend architecture principles
  • Familiarity with cloud infrastructure (AWS or GCP) and modern DevOps/CI-CD practices
  • Strong understanding of frontend performance optimization and rendering strategies (SSR, SSG, ISR)
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The Company
6 Employees
Year Founded: 2024

What We Do

Spangle AI builds an agentic commerce platform that connects AI-led product discovery with real-time conversion. Its software turns shopper context into adaptive shopping experiences, helping enterprise and direct-to-consumer brands improve conversion and return on ad spend. The company combines AI agents, commerce infrastructure, and tailored implementation services to help retailers protect brand equity, retain first-party data, and grow sustainably over time.

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