Senior Full-Stack Engineer (Founding Team)

About Celery Celery is an early-stage startup building an AI-native Payroll Operations platform to automate complex enterprise workflows and eliminate high-stakes manual processes. We have already built our foundational infrastructure and are looking for a highly capable, hands-on Senior Full-Stack Engineer to join us as a core member of our founding team to help us expand our platform.

The Role This is a pure execution role for a builder. We operate with flat hierarchies, high autonomy, and zero micromanagement. You will own features completely end-to-end: from initial architectural design and product validation through to production deployment.

We need an engineer who takes complete ownership of the system. You are the type of developer who engages with product requirements, challenges assumptions, and fixes underlying issues or edge cases before they ever become bugs in production. You do not wait for a ticket or a manager to tell you what to do.

Key Responsibilities:

Build and scale core backend services in Python, focusing on data pipelines, custom rule engines, and agentic workflow automation.
Develop clean, robust, and highly responsive user interfaces using React.
Collaborate directly with product management to shape both the technical architecture and the product direction.
Maintain a high bar for code quality, proactively addressing system friction points and optimizing performance.

Requirements:

6+ years of experience building complex, data-heavy, production-grade web applications.
Strong full-stack capabilities, with deep proficiency in Python on the backend and React on the frontend.
Experience designing data pipelines and handling multi-source data ingestion or unstructured data parsing.
Experience with LLMs, agentic workflows, or browser automation is a significant advantage.
A high-agency mindset: independent, resourceful, and capable of executing in a fast-paced, evolving startup environment.
Strong product sense and the communication skills to debate features and collaborate on product definitions.

What We Offer:

A founding-team equity package.
Direct impact on technology, product strategy, and engineering culture from day one.
A highly technical environment focused on solving genuine, complex automation problems.