Top Senior Software Engineer Jobs in St. Louis, MO

Lead design and implementation of backend systems for Model-Based Engineering web applications. Build APIs, data-processing and analytics pipelines, optimize SQL, develop production-ready infrastructure, create test suites, mentor engineers, participate in architecture and tech selection, and ensure scalability, resilience, and performance for large-scale distributed systems.

Develop, test, and maintain embedded software for defense systems. Translate customer requirements into software designs, perform unit/integration testing, support system integration, review peer work, create interface definitions and documentation, and follow software architecture and open-architecture principles.

Lead design, architecture, and development of simulation models and frameworks; author requirements and software designs; integrate hardware/software in lab environments; coordinate multi‑team priorities, perform design reviews, and mentor engineers; serve as customer‑facing SME for Flight Simulation Labs products and ensure delivery of high‑quality integrated simulation capabilities.

The Software Engineer will design and develop simulation software, perform testing and analysis, and support various engineering teams in simulation integration.

Lead design, architecture, and development of simulation models and frameworks for flight simulation. Own software architecture, requirements, implementation, integration, and testing. Coordinate across hardware teams and multiple scrum teams, mentor engineers, perform design reviews, and ensure delivery of secure, high-quality simulation products for an Air Dominance program.

Design, architect, and develop simulation models, virtual environments, and frameworks. Validate, integrate, modernize, and test simulation software and legacy systems, collect and process data, document algorithms and specifications, and collaborate with cross-functional teams to enable system integration and optimize performance in a secure Agile environment.

Design, develop, test, and maintain non-embedded software for the Tomahawk program. Translate requirements into software designs, implement features, troubleshoot issues, and document R&D. Ensure compliance with government and safety standards and support system integrations.

Design, build, and maintain secure, automated CI/CD pipelines and infrastructure for safety-critical software. Automate tooling, deploy and monitor releases, integrate security controls, analyze and mitigate vulnerabilities, support cross-functional teams, and implement emerging technologies to enable scalable, compliant software delivery for defense aircraft health management.

Design and implement CIAM backend services for authentication and authorization. Integrate identity systems, manage secure flows, and automate infrastructure.

Design, develop, test, and maintain embedded application software for air-domain missions. Translate customer requirements into software architecture, perform unit/integration testing, support system integration and verification, participate in peer reviews, and produce software documentation while meeting safety, regulatory, and customer standards.

Own and evolve the Subscriptions and Payments backend: design APIs, integrate providers, improve reliability and scalability, lead architecture and code reviews, collaborate cross-functionally, and participate in on-call rotations.

As a Billing & Analytics Software Engineer, you'll design and maintain the billing pipeline, integrate billing systems, and develop customer-facing analytics dashboards to support revenue recognition and operational observability.

Design, develop, test, and maintain full-stack web applications, databases, and data processing tools for fleet health analytics. Collaborate with stakeholders, lead and coordinate cross-team development, perform troubleshooting and debugging, improve processes and documentation, apply system-level thinking, and mentor junior engineers in a mission-critical aerospace environment.

Develop, test, and maintain mission-planning weapon software within a SAFe Agile scrum team. Translate requirements into designs, implement and integrate microservices (C#/C++ back end, JavaScript/TypeScript/React front end), debug issues, write documentation, and perform unit/integration/system-level testing and validation.

Maintain and improve GameChanger's backend API server and SDK. Implement API/SDK changes, improve developer ergonomics, optimize performance and scalability, design critical systems, document and mentor teammates, and participate in on-call rotation.

Design, implement, and maintain partner integration solutions; translate partner requirements into scalable technical implementations; troubleshoot and automate fixes; collaborate with product and engineering teams to improve tools and ensure successful partner onboarding and launches.

Lead design and delivery of scalable customer-facing features, services, and APIs that process real-time data and AI-powered insights. Build web experiences, contribute to LLM/AI workflows, ensure reliability through observability and rollout practices, and collaborate cross-functionally with Product, Design, ML, and platform teams.

Build and evolve Circle Discover marketplace features: high-converting purchasing flows, algorithmic recommendations, content feeds, and listings. Work across a Ruby on Rails backend and React/Next.js front-ends, optimize performance and SSR/SSG, collaborate with designers and leaders, and improve codebase quality while shipping at pace in a distributed remote team.

Build and operate high-throughput backend services powering AI agent orchestration, connector integrations, and real-time data pipelines. Design scalable core platform services, collaborate with ML, frontend, and product teams, implement infrastructure-as-code and CI/CD, and mentor junior engineers to deliver reliable, AI-powered features.

Design, develop, test, and maintain full‑stack web applications, databases, and data processing tools for model‑based sustainment simulations. Collaborate with stakeholders, lead or contribute to planning and code reviews, troubleshoot and optimize software, improve processes and documentation, and mentor junior engineers in an agile, mission‑critical aerospace environment.

Lead architecture, modernization, and development of Group Insurance applications. Modernize mainframe monoliths into Java microservices and micro-frontends on cloud, mentor distributed Agile teams, collaborate with enterprise architecture, product owners and infrastructure, and enable test automation and integrations. Approximately 10% domestic travel.

Build and own Eve's marketing site and GTM engineering stack: integrate and optimize external tools, design AI agents for sales and marketing, implement webhooks and middleware to sync product/CRM data, and create programmatic campaigns and internal tools in partnership with Marketing, Sales, RevOps, and Product to drive growth and automation.

Lead frontend-leaning full-stack implementation work for carrier and enterprise integrations: architect reusable UI and API layers, author RFCs, guide technical delivery, enforce testing and security best practices, and partner with cross-functional teams to scope and ship production integrations.

As a Senior Software Engineer in Trust & Safety, you'll analyze threats, design systems for abuse detection, and collaborate with teams to implement scalable defenses.

Design, build, and maintain scalable, reliable full‑stack systems. Contribute to API and architecture design, write testable code, debug complex issues, improve performance, automate deployments, and mentor junior engineers while collaborating with cross‑functional teams.