Senior Full Stack Developer- Python

REI Systems; United States; On-site; USD 110,000 - 160,000; Full time

Job summary

REI Systems in the United States is seeking a mid-senior Full Stack Developer to support modernization efforts for FDA projects. You will design, develop, and deploy secure enterprise applications across UI, backend, APIs, and cloud environments.

The ideal candidate combines strong frontend and backend software engineering skills with hands-on experience in RESTful services, data integrations, and Generative AI technologies, including RAG and LLM workflows, while collaborating with architects,

Qualifications

• Experience delivering full stack web applications for enterprise environments.
• Proven ability to design, implement, and test scalable software components.
• Hands-on experience integrating AI/LLM features (RAG, prompts, embeddings).

Responsibilities

• Full Stack Application Development: design, develop, test, and maintain secure, scalable enterprise web applications.
• Generative AI & LLM Solutions: build and support AI features and LLM workflows.
• RAG, Knowledge & Data Engineering: design data pipelines and integration with AI components.
• Frontend Engineering: create responsive, accessible web interfaces using modern JS/TS practices.
• Backend Services & Integration: develop backend services and APIs, ensure secure integrations.

Skills

Full stack development

Frontend engineering

Backend engineering

RESTful APIs

Python

TypeScript

AI/LLMs

Cloud environments

Security basics

Tools

Python

TypeScript

APIs

Cloud platforms

LLMs platforms

Job description

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 ap