Justin Sebastian

AI Engineer | Full-Stack Developer

Austin, TX

Full-stack software engineer with 10+ years building cloud-based applications on AWS. AI-first approach to development — building agentic AI systems, evaluation pipelines, and production LLM deployments to ship products serving 2M+ users.

Work Experience

Founder & AI Engineer

UofHappy, Jan 2019 - Present

Sole technical founder — owned product vision, architecture, and all engineering across 6 products serving 2M+ users using TypeScript, Python, and Laravel on AWS (EC2, Lambda, S3, RDS, CloudFront). Designed microservices architecture with DynamoDB, SQS, and Step Functions. Integrated generative AI across the product suite — RAG pipelines, agentic workflows, LLM-powered content generation, data pipelines, and adaptive learning systems. Built evaluation pipelines using DeepEval and Pytest to validate output quality and detect hallucinations, with LLM guardrails for input sanitization and prompt injection protection.

Zero to Hero — AI Education Platform (Web)

AI-generated interactive coding exercises with adaptive difficulty. Built with Python, FastAPI, and AWS Lambda.

365 Gratitude — Social Wellness Platform (iOS & Android)

Flagship product scaled to 2M+ users. Social feed with user interactions, dynamic affirmations, and quizzes that drive personalized guidance powered by LLMs.

Insight Books — AI Learning Platform (iOS & Android)

RAG pipeline with sliding-window chunking, structural metadata filtering, and LLM-as-judge evaluation. LangChain orchestration with LangSmith tracing for end-to-end observability.

UofHappy — Adaptive Learning Platform (iOS & Android)

Agentic content generation pipeline (research → author → audit) with knowledge graphs and personalized learning paths that adapt to user progress.

Wise Journal — AI Journaling App (iOS & Android)

Multi-layer RAG with dual embedding architecture (semantic + thematic) for long-term pattern retrieval across unstructured journal entries.

Zero Meditation — AI Meditation App (iOS & Android)

On-demand personalized guided meditations via async chunked LLM generation with SSML enrichment for zero-latency audio delivery.

Senior Solutions Consultant

Sirius Computer Solutions, 2015 - 2018

Built cloud-based software for Fortune 500 clients, from scoping technical requirements to shipping production systems. Owned microservice and API architecture across multiple engagements, partnering with engineering teams to optimize AWS infrastructure.

Solutions Consultant

Avnet Technology Solutions, 2014 - 2015

Built proof-of-concept applications and led technical discovery for complex multi-system integrations. Gathered requirements from stakeholders and delivered software solutions for enterprise clients.

Technical Program Analyst

Waste Management, 2012 - 2014

Managed technical programs across engineering and operations teams using Agile/Scrum methodology and JIRA. Coordinated sprint planning, backlog prioritization, and release tracking for enterprise system upgrades. Analyzed requirements, defined technical scope, and kept cross-functional teams aligned on deliverables.

Education

University of North Carolina, Chapel Hill

Bachelor's Degree, 2008 - 2012

Certifications

Deep Learning Specialization

Coursera · Mar 2018

Artificial Intelligence Nanodegree

Udacity · Jan 2018

Skills

Languages & Frameworks

Python, TypeScript, PHP, JavaScript, Node.js, Java, React, Angular, Flutter, FastAPI, SQL

Cloud & Infrastructure

AWS (EC2, Lambda, S3, SQS, RDS, CloudFront, SageMaker, Kinesis, Step Functions, DynamoDB), Azure, Docker, CI/CD, PostgreSQL, MS SQL

AI & LLM Engineering

LLMOps, RAG Systems, Embeddings, Vector DB, Agentic AI, Prompt Engineering, LLM Evaluation, LangChain, LangSmith, DeepEval, Bedrock, Vertex, Foundry

AI Development & Automation

Claude Code, Cursor, GitHub Copilot, Zapier, Make, n8n, Langflow, Flowise