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# Senior Fullstack Engineer

- **Company:** Phaxis LLC
- **Location:** El Segundo, CA, United States
- **Experience:** Expert
- **Salary:** $150,000.0 - $175,000.0
- **Contract:** Permanent contract
- **Skills:** LangGraph Framework, AI Evaluation, JavaScript (Programming Language), PHP (Programming Language), Application Programming Interfaces (APIs), Artificial Intelligence, Databases, Software Debugging, Information Retrieval, Python (Programming Language), Machine Learning, NoSQL, Svelte, Software Deployment, SQL Databases, Web Application Frameworks, ReactJS, Large Language Models, Backend, Agentic-AI, Vue.js, AngularJS, Production Code, Front End Software Development, Virtual Agents, Model Context Protocol
- **Published:** October 27, 2026
- **Apply:** https://www.careerbuilder.com/job-details/senior-fullstack-engineer-el-segundo-ca--b8c9fbec-8f62-4096-91e1-01c087aca26f

## About the Role

Artificial Intelligence (AI), Ecosystems, Artificial Intelligence (AI) Agents, Project Lifecycle, MCP - Microsoft Certified Professional, Software Agents, Performance Analysis, Continuous Improvement, Problem Solving Skills, Root Cause Analysis, Foundation (Required):
5+ years shipping production code (frontend and backend)
Strong programming fundamentals: We'll primarily use JavaScript, Python and PHP, but
value problem-solving skills over specific language expertise
Backend development experience: Building workflows, APIs, state management, and
async systems
Database knowledge: Working with both SQL and NoSQL databases
Frontend skills: Building responsive interfaces with modern frameworks (React, Vue,
Angular, Svelte, etc.)
Experience applying AI/ML in production: You've worked with LLMs or ML models in real
applications, not just tutorials
Working Style:
Ownership mindset: You identify problems, take initiative, and see things through
Pragmatic and adaptable: You choose the right tool for the job and aren't afraid to learn
new technologies
Systematic problem-solver: You can debug complex systems and think through tradeoffs
Good to Have:
Knowledge of AI evaluation, error analysis, and building feedback loops
Experience with agentic frameworks (LangGraph, Google ADK) or Model Context
Protocol (MCP)
Background in information retrieval or search systems

## Description

Our client is looking for a Senior Fullstack Engineer to join our Agentic AI team. You'll help
build our AI capabilities from the ground up, designing and shipping tools, services, and intelligent
agents that power AI experiences across our entire product ecosystem.
What You'll Do
Build and ship full-stack AI applications: Create frontend experiences and backend
systems that power real AI capabilities, iterating based on performance and user
feedback
Own the full lifecycle: Take projects from idea through production deployment, ensuring
quality, reliability, and scalability
Build foundational infrastructure: Develop search/retrieval services, tool execution layers
(MCP servers), workflows, and intelligent agents
Establish measurement systems: Create feedback loops and performance tracking to
continuously improve AI system behavior
Solve complex problems: Debug issues across the stack, identify root causes, and
implement robust solutions