Senior Full-Stack Software Engineer

About the role

Senior Full-Stack Software Engineer — Python, Java, Rust, C#, C++

Location: United States | Remote

Commitment: Full-time | 40 hours/week

Employment: W-2 through Cincinnatus LLC

Compensation: $90–$110/hour

About the Role

An opportunity is available for experienced Senior Full-Stack Software Engineers to support a leading AI lab's GenAI team in building and testing software on top of advanced AI models.

You'll build, integrate, and stress-test real applications using technologies including Python, Java, Rust, C#, C++, and TypeScript. The work involves integrating pre-release model APIs into production-style software, developing evaluation infrastructure and internal tools, and identifying model and integration failure modes.

Engineers will work directly with the team's engineering manager on fast-moving projects and are expected to onboard quickly and contribute working code early.

Key Responsibilities

Build and ship full-stack applications, services, and internal tools using Python, Java, Rust, C#, C++, or TypeScript

Integrate pre-release model APIs into working software, including tool interfaces, evaluation harnesses, and telemetry

Diagnose and document model and integration failure modes discovered during development

Translate engineering observations into clear technical feedback for research teams

Prototype quickly against evolving requirements and deliver working increments with limited up-front specification

Collaborate with engineering leadership and other engineers to maintain code quality, architecture, and technical documentation

What We're Looking For

6+ years of professional experience building and shipping production software at a recognized, top-tier organization, including end-to-end ownership of systems

Deep production experience in at least one of Python, Java, Rust, C#, or C++, plus demonstrated delivery experience in a second language across a different ecosystem

Hands-on ownership across the full stack, including backend service and API design, modern front-end frameworks such as React, data modeling, and cloud deployment and operations

Demonstrated ability to onboard onto unfamiliar codebases and deliver working code quickly with minimal ramp-up

Demonstrable career progression

Ability to reliably commit at least 40 hours/week during weekdays

Strong written communication skills and ability to clearly explain complex technical decisions

Application Process

Click Apply to continue to the external application platform

Review and accept the referral invitation associated with the application

Register or sign in as required

Complete the required application steps and assessments

Qualified applications will be reviewed for the opportunity

Applicants must complete the required application process and assessments on the external platform to be considered.

Employment

This is a W-2 employment position with Cincinnatus LLC, with the opportunity to be placed at a leading AI lab as part of its extended workforce.

Cincinnatus LLC serves as the employer of record for the engagement and provides W-2 employment, payroll, benefits, and compliance.

Equal Employment Opportunity

Cincinnatus LLC is an Equal Employment Opportunity employer. Qualified applicants are considered without regard to legally protected characteristics, and reasonable accommodations are available upon request.

Core Skills: Full-Stack Engineering, Python, Java, Rust, C#, C++, TypeScript, React, API Design, Data Modeling, Cloud Deployment, AI/LLM Integration, Software Architecture

Referral note: This role is shared through a referral program, and I may receive a referral reward for successful hires.