Senior Full-Stack Developer – Python

Overview REI Systems’ mission is to deliver reliable, innovative technology solutions that advance Federal clients' missions and exceed their expectations. Our technologists and consultants are passionate about solving complex challenges that impact millions of lives. We take a Mindful Modernization® approach in delivering our services, including application modernization, grants management, case management systems, government data analytics, and advisory services. This approach, the REI Way, ensures mission impact by aligning our clients' strategic objectives with measurable outcomes through people, processes, and technology. We offer the same commitment to our employees by providing professional development, meaningful projects, and flexibility to spend time with family and friends. We believe employees are at their best when fulfilled in both their professional careers and their personal lives. Learn more at www.REIsystems.com. Employees voted REI Systems a Washington Post Top Workplace in 2015, 2016, 2018, 2020, 2021, 2022, 2023, 2024, and 2025! Responsibilities Position Overview REI Systems is seeking a mid-senior Full Stack Developer to support technology modernization and digital transformation initiatives for the FDA. The Full Stack Developer will design, develop, integrate, test, deploy, and support secure enterprise applications across the user interface, backend services, APIs, databases, and cloud environments. The ideal candidate combines strong frontend and backend software engineering skills with practical experience building modern web applications, RESTful services, and data integrations. This role is intended for a hands-on engineer who can independently own complex application features while collaborating with architects, product owners, testers, DevOps engineers, database administrators, and business stakeholders. Responsibilities Full Stack Application Development Design, develop, test, and maintain secure, scalable enterprise web applications that address business and operational requirements.Develop end-to-end application features spanning user interfaces, backend services, APIs, business logic, and data persistence.Translate functional and technical requirements into maintainable application components and reusable software patterns.Modernize and enhance existing applications while maintaining compatibility with enterprise architecture and integration standards.Troubleshoot application defects, integration failures, performance issues, and production incidents throughout the development lifecycle.Develop proof-of-concepts and technical prototypes and transition successful solutions into production-ready capabilities. Generative AI & LLM Solutions Develop applications leveraging Large Language Models (LLMs) and Generative AI technologies.Build and support Retrieval-Augmented Generation (RAG) solutions using enterprise documents, structured data, and approved knowledge sources.Implement prompt engineering, prompt templates, grounding, context management, tool/function calling, and structured LLM outputs.Integrate commercial and/or open-source LLMs through APIs and enterprise AI platforms.Work with embeddings, semantic search, vector databases, reranking, chunking strategies, and document-processing pipelines.Develop AI-enabled capabilities such as intelligent search, summarization, classification, information extraction, question-answering, and workflow automation.Implement appropriate guardrails, monitoring, fallback strategies, and human-in-the-loop processes for Generative AI applications. RAG, Knowledge & Data Engineering Design ingestion and retrieval pipelines for enterprise documents and data sources used by AI/LLM applications.Develop data preprocessing, cleansing, transformation, chunking, metadata enrichment, and validation routines.Work with relational databases, APIs, document repositories, object storage, search platforms, and cloud-based data services.Collaborate with data engineers to establish reliable, governed data pipelines for AI/ML use cases.Ensure appropriate handling of data quality, lineage, security, access controls, and source traceability. Frontend Engineering Develop responsive, accessible, and user-friendly web interfaces using modern JavaScript/TypeScript practices and component-based frameworks.Implement client-side validation, state management, error handling, and reusable user-interface components.Integrate frontend applications with RESTful APIs and enterprise services using secure authentication and authorization patterns.Collaborate with product owners, UX/design resources, and testers to ensure application behavior aligns with user and business needs.Support accessibility and usability requirements applicable to federal web applications, including Section 508 considerations. Backend Services & Integration Develop backend services and business logic using Python technologies appropriate to the application architecture.Design, develop, document, and maintain RESTful APIs and microservices for internal and external integrations.Implement secure service-to-service communication, input validation, exception handling, logging, and transaction management.Integrate applications with relational databases, enterprise APIs, document repositories, and cloud-based services.Collaborate with architects and integration teams to support reliable interoperability across enterprise systems. Data & Database Development Design and work with relational data models that support application functionality, reporting, and integration needs.Write, optimize, and troubleshoot SQL queries and data-access logic for performance, reliability, and maintainability.Collaborate with database administrators on schema changes, indexing, data migration, security, and production support.Apply appropriate data validation, integrity, access-control, and error-handling practices within application workflows. Cloud, DevSecOps & Deployment Develop and deploy application components in AWS and/or Azure environments in collaboration with cloud and DevOps engineering teams.Participate in CI/CD processes for automated build, testing, security scanning, deployment, and release management.Containerize application services using technologies such as Docker and support deployment in cloud-native environments.Use application logging, metrics, tracing, and monitoring to support troubleshooting, operational readiness, and performance improvement.Apply secure software development and DevSecOps practices across the application lifecycle. Software Quality & Agile Delivery Develop clean, maintainable, testable, and reusable code following established software engineering standards and design principles.Create and maintain unit, integration, API, and automated tests appropriate to the application stack.Participate in code reviews, peer reviews, technical design discussions, and defect resolution.Work within Agile/Scrum teams and participate in sprint planning, backlog refinement, demonstrations, and retrospectives.Maintain technical documentation for application architecture, interfaces, configurations, deployment, and operational support. Application Security & Federal Compliance Follow applicable federal and FDA security, privacy, data-governance, and software development requirements.Apply secure coding practices for authentication, authorization, input handling, secrets management, data protection, and API security.Support remediation of application security findings identified through code scanning, dependency scanning, penetration testing, or security reviews.Participate in technical reviews and provide documentation required for production deployment and operational support. Qualifications Approximately 5-8 years of professional software development experience, including hands-on full stack application development.Strong backend development experience with Python, Java and/or .NET technologies and enterprise application patterns.Strong frontend development experience with JavaScript/TypeScript, HTML, CSS, and a modern component-based web framework.Experience designing, developing, and integrating RESTful APIs and backend services.Working knowledge of SQL, relational databases, data modeling, and application data-access patterns.Experience with Git, branching strategies, code reviews, and modern software development practices.Experience with unit testing, integration testing, automated testing concepts, and defect troubleshooting.Working knowledge of CI/CD pipelines and application deployment practices.Experience working in Agile/Scrum multidisciplinary development environments.Strong analytical, troubleshooting, and problem-solving skills.Ability to communicate technical concepts clearly to technical and non-technical stakeholders. Preferred Qualifications Experience supporting FDA, HHS, or other federal government programs.Experience developing and deploying enterprise applications in AWS or Azure.Experience with frontend frameworks such as React or Angular.Experience with backend frameworks such as FastAPI, Spring Boot, ASP.NET Core, or comparable enterprise frameworks.Experience with Docker and containerized application deployment; familiarity with Kubernetes or cloud-native platforms.Understanding of microservices, event-driven integration, and enterprise application architecture.Experience with OAuth 2.0, OpenID Connect, role-based access control, and API security patterns.Familiarity with application performance monitoring, distributed tracing, logging, and observability practices.Familiarity with DevSecOps practices, dependency management, static analysis, and secure software development.Experience supporting Section 508 accessibility and federal web application requirements.Experience working with sensitive, regulated, scientific, healthcare, or federal data is a plus. Professional Skills Strong analytical and critical-thinking abilities.Excellent written and verbal communication skills.Ability to translate business and user requirements into practical technical solutions.Ability to independently own complex development tasks and features while collaborating effectively within a larger technical team.Strong attention to detail and commitment to software quality, security, maintainability, and user experience.Ability to work across multiple technology layers and troubleshoot issues from the user interface through backend services and data stores.Ability to communicate technical risks, assumptions, dependencies, and recommendations clearly.Strong documentation, mentoring, and knowledge-sharing skills. Key Technologies Languages: Python, Java and/or C#, JavaScript/TypeScript, SQL Frontend: React and/or Angular, HTML, CSS Backend: FastAPI, Spring Boot and/or ASP.NET Core, REST APIs, microservices Cloud: AWS and/or Azure Development: Git, CI/CD, Docker, automated testing Data: SQL databases, enterprise APIs, structured data Methodology: Agile/Scrum, DevSecOps Ideal Candidate Profile The successful candidate will be a hands-on full stack developer who is comfortable moving across the application stack rather than working exclusively in frontend or backend development. They should be able to build user-facing features, implement backend services and APIs, work with relational data, troubleshoot integration issues, and collaborate with cloud and DevOps teams to deliver secure production applications. This individual should have sufficient experience to independently own complex features and technical tasks, contribute to design decisions and code reviews, and mentor less-experienced developers while operating under the broader technical direction of solution architects and program leadership. Education: Bachelor’s degree in computer science or a related field. Clearance: Candidate must be able to obtain and maintain a Clearance. Location: Hybrid (2 Day per week in our Sterling, VA HQ) EEO Statement: REI Systems is an Equal Opportunity Employer.