João Guedes

Professional Summary

Software Engineer specializing in Go (Golang), distributed systems, and Unix-like environments. Experienced building scalable, production-grade microservices using gRPC, Kafka, and asynchronous processing, with strong focus on performance, reliability, and clean system design. Hands-on experience with OCR-based invoice processing, API integrations, and automated payment workflows (PIX). Comfortable working close to the system across Linux and BSD, with containerization, filesystem management, and backend performance optimization.

Technical Skills

• Languages: Go (Golang), Python, Shell (bash/ksh/zsh), Clojure, Haskell, Node.js
• Backend: gRPC, REST, Gin, Kafka, Asynq, Protocol Buffers, WebSockets, JWT Authentication
• Distributed Systems: Microservices, event-driven design, job queues, caching (Redis), concurrency, connection pooling
• Systems & Infrastructure: Linux, FreeBSD, OpenBSD, Docker, Podman, FreeBSD jails, OpenSSH, AWS S3/Lambda/EC2, MinIO, ZFS, ext4, XFS
• Frontend: React, Vue.js
• Databases: PostgreSQL, MySQL, MongoDB; SQL query optimization
• AI & OCR: Mistral OCR, OpenCV, pyzbar, statistical analysis
• DevOps: CI/CD pipelines, deployment automation, infrastructure as code
• Principles: UNIX philosophy, KISS, minimalism, open-source

Professional Experience

Backend Engineer | AxxisPay | Campinas, SP, Brazil | Jan 2024 – Present

• Developed production-grade Go (Golang) backend modules for a shopping application, supporting the ingestion and processing of ~2,000 invoices per day through automated workflows.
• Implemented S3-compatible object storage using MinIO, processing and storing 57k+ invoice images and PDFs since July.
• Built a Python computer vision microservice for restricted product detection, achieving 99.6% accuracy across 5,646 real-world invoices, significantly reducing manual compliance review.
• Designed an asynchronous Brazilian fiscal document processing system (NFC-e, NF-e, CF-e-SAT) using QR codes, barcode extraction, and Mistral OCR + OpenCV, keeping user-facing flows non-blocking.
• Developed a Go-based NFC-e fiscal data scraper with direct integration to Secretaria da Fazenda systems, automating fiscal data retrieval previously done manually.
• Architected dynamic search APIs in Go, supporting 20+ filter combinations with sub-second response times.
• Integrated WPS Parking API with OCR-assisted reconciliation, reducing payment mismatch errors by ~70%.
• Integrated ingresso.com APIs for movie listings and ticket purchasing, supporting thousands of daily requests.
• Implemented indirect automated PIX payment processing with seconds-level settlement latency.
• Containerized and deployed services using Docker on Railway, performing database schema and query optimizations.

System & Automation Projects | Personal / Open Source | 2021 – Present

• Wrote technical articles on my personal website covering OpenBSD system administration and Golang best practices, sharing practical experiments and lessons learned.
• Developed a ZFS filesystem monitoring system using gRPC, with server-side logic in Elixir, exploring cross-language RPC and observability concepts.
• Built a peer-to-peer media streaming application in Go with concurrent downloads and optional subtitle handling, focusing on networking and concurrency.
• Created a JWT-based authentication service in Go using Gin, including password hashing and HTTP-only sessions, as a secure API reference implementation.
• Maintained a personal repository of reusable code snippets and automation tools across Shell, Python, Go, C, and Clojure.
• Developed a Go ↔ Python interoperability library for cross-runtime execution and automation scenarios.
• Contributed C utilities and OpenBSD Ports, focusing on system-level tooling and BSD ecosystem practices.
• Wrote shell automation scripts for system tasks such as monitors and desktop utilities.
• Developed a Haskell-based tool to manage and regenerate my static technical blog.

Data Science & AI Projects | University / Personal | 2024 – Present

• NoSQL chatbot using Flask + PyMongo with frontend in ClojureScript.
• Developed Go and Python APIs for agentic automation tasks.
• Built statistical tools and data processing pipelines for academic research.

Education

Bachelor of Data Science & AI | PUC-Campinas | 2024 – Present

Additional Interests

• UNIX systems, privacy, digital minimalism, open-source advocacy.
• Contributor and enthusiast of BSD systems (FreeBSD/OpenBSD).
• Functional programming (Clojure, Haskell) and type-driven development.
• Distributed systems, queue architectures, and backend performance engineering.
• Writer of technical articles at fugu.cafe.