Senior Fullstack Engineer

SpangleAI; Bellevue (WA); On-site; USD 170,000 - 230,000; Full time

Benefits offered by this job

Health insurance

401(k)

Unlimited PTO

Equity

Job summary

SpangleAI in the United States is seeking a Senior Fullstack Engineer with deep client-side expertise to help build our next-generation merchant experience platform. You will own frontend SDK development, multi-tenant architecture, and enterprise integration frameworks.

You’ll work with React, Next.js, and Tailwind to deliver high-performance web apps, collaborate with backend teams over REST/GraphQL, and shape performance, accessibility, and scalable deployment practices across AWS/GCP.

Qualifications

• 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.

Responsibilities

• Client-Side Platform & SDK Development: Design and implement reusable, distributed JavaScript/CSS SDK frameworks for merchant integration across diverse environments.
• Frontend Engineering: Build high-performance web apps with React, Next.js, and Tailwind CSS, using SSR/SSG/ISR for SEO and speed.
• API & Backend Integration: Collaborate with backend teams to connect frontend logic to REST/GraphQL services and ensure secure communication.
• Performance & Scalability: Drive optimizations via code splitting, lazy loading, caching and runtime efficiency.
• Code Quality & Standards: Write clean, accessible, modular code and implement automated tests.

Skills

JavaScript

TypeScript

React

Next.js

Tailwind CSS

REST APIs

GraphQL

Performance optimization

Multi-tenant architectures

SDK development

Tools

AWS

GCP

CI/CD

Testing & QA tooling

Job description

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.

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

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.