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

Senior Full-Stack Software Engineer — Python, Java, Rust, C#, C++Location: United States | RemoteCommitment: Full-time | 40 hours/weekEmployment: W-2 through Cincinnatus LLCCompensation: $90–$110/hourAbout the RoleAn 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 ResponsibilitiesBuild and ship full-stack applications, services, and internal tools using Python, Java, Rust, C#, C++, or TypeScriptIntegrate pre-release model APIs into working software, including tool interfaces, evaluation harnesses, and telemetryDiagnose and document model and integration failure modes discovered during developmentTranslate engineering observations into clear technical feedback for research teamsPrototype quickly against evolving requirements and deliver working increments with limited up-front specificationCollaborate with engineering leadership and other engineers to maintain code quality, architecture, and technical documentationWhat We're Looking For6+ years of professional experience building and shipping production software at a recognized, top-tier organization, including end-to-end ownership of systemsDeep production experience in at least one of Python, Java, Rust, C#, or C++, plus demonstrated delivery experience in a second language across a different ecosystemHands-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 operationsDemonstrated ability to onboard onto unfamiliar codebases and deliver working code quickly with minimal ramp-upDemonstrable career progressionAbility to reliably commit at least 40 hours/week during weekdaysStrong written communication skills and ability to clearly explain complex technical decisionsApplication ProcessClick Apply to continue to the external application platformReview and accept the referral invitation associated with the applicationRegister or sign in as requiredComplete the required application steps and assessmentsQualified applications will be reviewed for the opportunityApplicants must complete the required application process and assessments on the external platform to be considered.EmploymentThis 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 OpportunityCincinnatus 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 ArchitectureReferral note: This role is shared through a referral program, and I may receive a referral reward for successful hires.