Senior Full Stack Engineer - Agent Experience

NinjaTech AI; Sydney; On-site; AUD 180,000 - 240,000; Full time

Job summary

NinjaTech AI is seeking a senior full-stack engineer in Sydney to own end-to-end slices of the agent experience, from UI to backend services. You will ship agent-facing features with reliability and observability, and iterate quickly based on usage data.

We value strong TS/React and Python depth, product instincts, and comfort with rapid change and incomplete specs. Work includes Next.js/React, FastAPI, Postgres, and AWS containerised environments.

Qualifications

• 5+ years building and operating full-stack products in production.
• Strong TS/React and backend depth in Python; design schemas and debug slow queries.
• Product instincts to shape features, not only implement tickets.
• Comfort with high change rates and incomplete specs for agentic products.

Responsibilities

• Own end-to-end slices of the agent experience — UI, API and backend services behind them.
• Ship agent-facing features into production with reliability, latency and observability.
• Turn ambiguous product bets into working software quickly and test against usage data.
• Collaborate with AI and science engineers on tool behavior, context and streaming in the product.

Skills

Full-stack production

TypeScript/React

Python (FastAPI)

Product intuition

Observability basics

Tools

Next.js

FastAPI

Postgres/Supabase

AWS CDK

ECS/Lambda

Containerization

Job description

Sydney

• Full-time
• On-site/hybrid

SuperNinja is an AI workforce that plans, writes code, runs research and ships real work for customers. You would own the surface where people meet that agent — the thread, the workspace, the moment a task becomes a deliverable. It is the highest-visibility slice of the product and it changes weekly.

What You'll Do

• Own end-to-end slices of the agent experience — UI, API and the backend services behind them, not just the frontend of someone else's endpoint.
• Ship agent-facing features into production continuously and stay on them: reliability, latency, incidents, observability.
• Turn ambiguous product bets into working software in days, then decide from usage data whether to double down or delete it.
• Work directly with our AI and science engineers on how tools, context and streaming behave in the product.

What We're Looking For

• 5+ years building and operating full-stack products in production.
• Strong TypeScript/React (we run Next.js) and genuine backend depth in Python (FastAPI) — you can design a schema and debug a slow query, not only call an API.
• Product instinct: you argue about the shape of the feature, not only the ticket.
• Comfort with high change rates and incomplete specs. Agentic products do not hold still.

Stack: Next.js/React/TypeScript, Python/FastAPI, Postgres/Supabase, AWS (CDK, CloudFront, ECS, Lambda, Cognito), containerised agent sandboxes.