Ruan – LLM, Python, RAG, experts in Lemon.io

Ruan

From Brazil (UTC-3)flag

AI Engineer|Senior
AI Agent Architect|Senior

Ruan – LLM, Python, RAG

Ruan is a Senior AI Engineer and Agent Architect with ~5 years of industry experience and unusually deep pre-GenAI NLP research roots — including an MSc in AI (Language Technologies) at the University of the Basque Country and University of Malta, 3 international shared task wins, and a published BM25 retrieval paper. He covers the full AI engineering stack: multi-agent systems in LangGraph, RAG pipelines, LLM-based document processing, vector search, and production fine-tuning on GPU clusters. He has shipped across fintech, government document processing, and open-source NLP tooling, and consistently ties architectural decisions to measurable business outcomes.

6 years of commercial experience in
AI
Fintech
Open source
Enterprise software
Main technologies
LLM
2.5 years
Python
5 years
RAG
2 years
LangChain
2 years
LangGraph
2 years
Hugging Face
3 years
Vector Databases
2 years
Prompt engineering
2 years
Additional skills
AI
Multi-agent systems architecture
GCP
Microsoft Azure
LlamaIndex
Pinecone
Weaviate
Neo4j
CI/CD
Vertex AI
PyTorch
MLOps
Direct hire
Possible
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Experience Highlights

AI Engineer
Aug 2025 - Jun 20269 months
Project Overview

Three Azure-based commercial AI pilots for a large enterprise software client: automated document-type classification, OCR/LLM extraction, and stakeholder-facing review tooling. Covered a workflow processing 1M+ annual applications, from evaluation setup through production deployment and engineering handoff.

Responsibilities:
  • Automated document-type screening with Azure Document Intelligence and LangChain, producing structured outputs with 95%+ accuracy.
  • Course-corrected an underperforming OCR/LLM extraction pilot by building evaluation benchmarks and identifying Azure AI Foundry alternatives capable of 90%+ field-level accuracy.
  • Built React-based reviewer tools, converted 40+ field corrections into prompt updates, deployed to Azure VM environments, and mentored 2 SWEs through 10+ knowledge-transfer sessions.
Project Tech stack:
Python
LangChain
Microsoft Azure
React
AI Engineer
Jan 2025 - Jul 20255 months
Project Overview

Product and technical delivery for a 6-month RAG proof of concept at a fintech platform processing 20% of all invoices issued in Brazil.

Responsibilities:
  • Accelerated Weaviate vector indexing by 99%+ by replacing full-corpus retrieval with partitioned searches, discovered through BigQuery invoice data analysis.
  • Optimized retrieval and ranking to 90%+ recall while cutting candidate depth from top-100 to top-20 — surfacing relevant matches with 80% fewer candidates.
  • Interviewed 10+ candidates and mentored 1 SWE to enable the transition from successful PoC to production.
Project Tech stack:
GCP
Weaviate
BigQuery
Vertex AI
AI Engineer
Sep 2023 - Jan 20251 year 4 months
Project Overview

AI system suite for a Brazilian digital bank serving 30M+ customers, comprising a LangChain/LangGraph GenAI sales agent for card upgrades, a BigQuery-driven lead qualification pipeline, and a RAG-based bank product Q&A system — covering the full lifecycle from lead selection through conversational AI to product information retrieval.

Responsibilities:
  • Developed a GenAI card-upgrade sales agent with LangChain and LangGraph, launching a 300+ user production pilot that cut customer acquisition cost by 6x while matching human-operator conversion rates.
  • Used BigQuery analytics and time-series modeling to identify low-friction upgrade leads and feed qualified users into the AI workflow.
  • Rescued an underperforming RAG system, beating OpenAI-based accuracy benchmarks and reducing inference costs by 90% through retrieval and prompt engineering improvements.
Project Tech stack:
Python
LangChain
LangGraph
GCP
BigQuery
AI Engineer
Aug 2020 - Apr 20221 year 7 months
Project Overview

AI research and open-source NLP tooling across three organizations (one later acquired by Hugging Face), covering embedding-based annotation workflows, weak supervision, semantic similarity, legal entailment, sentiment analysis, and retrieval systems.

Responsibilities:
  • Built Sentence Transformers + FAISS weak-labeling workflows with Snorkel, raising rule coverage from 32% to 79% and downstream model accuracy to 86%.
  • Implemented embedding-based annotation features and contributed 68K+ lines of production-ready open-source code.
  • Won 3 international NLP shared tasks in legal entailment, semantic similarity, and aspect-based sentiment analysis, beating runner-up teams by up to 6.4 F1 points.
Project Tech stack:
Python
Hugging Face
PyTorch
NLP

Education

2021
Computer Science
Bachelor's degree

Languages

Portuguese
Advanced
English
Advanced

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