Jason Fitzpatrick — Senior / Staff Engineer

Selected work

Rat Labs is my independent engineering studio — contract work and internal products I actually ship.

Rat Labs — internal

Tooling to help founders pressure-test ideas before spending six months on the wrong thing. Go + Rust Leptos.

Go Rust Leptos B2B SaaS

client

An AI shopping agent — tool calling, memory, multi-step reasoning against real inventory in production. Built and shipped the LLM framework from scratch. Go + Python, AWS Lambda/ECS.

Go Python AWS AI / LLM

Purcent

client · Boost Phase Ventures

Variable comp platform. Joined at the idea stage, built the full stack, and got it to paying enterprise customers. Go/Gin, React/TypeScript, AWS. The meetings were short.

Go React TypeScript AWS

Loop.baby

E-commerce subscription platform for baby products. Built backend services, integrated Stripe, BigCommerce, Klaviyo, and Segment.

Java Go AWS Lambda

CSI Companies

Built the internal publishing platform for Chick-fil-A's Menu DNA content system. Created OpenAPI clients and deployed serverless infrastructure.

AWS Lambda Docker Chick-fil-A

Seller Labs

Led a six-person team through a full PHP-to-Java rewrite of the core platform. Built Stripe billing for 200,000+ users.

Java AWS Team lead

About

I spent 14 years in the U.S. Army as a Logistics Officer — Captain, deployed to OIF III — then spent the next decade building software. That background probably explains why I like owning systems end to end and am not particularly afraid of things being on fire.

Originally from Georgia, moved to Castellón de la Plana in early 2024 with my wife. Our son was born here. The weather is absurd by any Midwestern standard, and I'm slowly picking up the language.

These days I work under the Rat Labs banner: contract work plus internal products I actually believe in. Backend-heavy: distributed systems, AI agent architecture, B2B SaaS. Go is my default, Java when the job calls for it, Python and TypeScript when I need to.

Castellón de la Plana, Spain