Guilherme Santos

Senior Software Engineer · Go Specialist · Freelancer

I am a Senior Software Engineer with 15+ years of experience, specializing in backend development with Go—my primary and preferred language since 2015. I’ve designed and built distributed systems, microservices, and event-driven architectures across multiple industries including fintech, e-commerce, and AI platforms.

I enjoy working on greenfield projects and have led personal initiatives such as an ERP for SMEs with e-invoicing and a multi-currency investment tracker. My open-source contributions include well-known projects like gRPC-Gateway and Elastic’s Go client.

Beyond backend development, I’m comfortable across the stack—from infrastructure (Kubernetes, Terraform, CI/CD) to frontend when needed. I bring a product mindset, clean code, and strong communication skills. Currently open for freelance and consulting opportunities focused on Go-based systems, cloud-native apps, and high-performance backend platforms.

Experience

Head of Engineering

Birdie AI

Led and restructured the engineering team, rebuilt the entire data pipeline, and launched a feedback intelligence platform powered by LLMs (e.g., ChatGPT) and fine-tuned custom models. Architected the system from scratch with Go microservices using an event-driven design over Google Pub/Sub, ElasticSearch, and Postgres. Drove engineering excellence, improved delivery processes, and enabled scalable AI-powered insights for enterprise customers.

May 2023 - Present

Staff Engineer

Qonto

Contributed to the evolution of Qonto’s backend architecture by defining new Go development standards, mentoring teams, and leading the rollout of a scalable, event-driven architecture. Worked closely with cross-functional teams to align technical decisions with business goals in a high-growth fintech environment

May 2022 - May 2023

Senior Software Engineer

Zalando

Modernized the Campaign and Content Solution (CCS) platform by designing and building Go-based microservices to replace a legacy PHP system. Migrated from SOAP to RESTful APIs and introduced Kafka-driven, event-based architecture to support better scalability and maintainability. Also developed a critical service for onboarding product articles from partners and internal teams like logistics and supplier ops.

June 2020 - April 2022

Founder & Lead Engineer

Giox Tecnologia

Founded and built a SaaS ERP platform for small businesses, later evolving it into a certified Brazilian e-invoicing system. Designed the architecture, developed the full stack, and managed DevOps to support scalability and automation. Originally built as a PHP monolith, the platform was re-architected into Go and PHP microservices with NSQ, MongoDB, and Vue.js. Developed a modern SPA frontend with Vuetify and Firebase, and managed infrastructure with Docker, Ansible, and GitLab CI.

March 2013 - Present

Senior Software Engineer

ProShare by Volkswagen

Developed the backend for a B2B car-sharing platform within the Volkswagen Group, focused on professional users. Built Go-based microservices with gRPC for inter-service communication, and exposed both GraphQL and REST APIs for mobile and web clients. Designed and deployed cloud-native infrastructure on AWS using Terraform and Kubernetes.

November 2019 - June 2020

Senior Software Engineer

DeliveryHero

Played a key role in modernizing Pandora’s platform (Foodora + Foodpanda), migrating a legacy PHP monolith to Go microservices with an event-driven architecture. As part of the Search & Discovery team, built a high-traffic API used by four brands across 20 countries, improving average response times by 6× using ElasticSearch, Redis, and MySQL. Promoted Go adoption across the organization by defining engineering standards, delivering training, and co-developing a new open-source library.

January 2018 - November 2019

Technical Lead

Ridelink

Led a polyglot engineering team in building a car-sharing platform, primarily using PHP (Symfony, Silex), with some services in Go and Python. Designed and deployed AWS-based infrastructure leveraging ECS, SQS, SNS, RDS, ElasticCache, and ElasticSearch. Built and open-sourced a CLI tool, deploy-ecs, to automate continuous deployments across environments.

September 2016 - December 2017

Education

UNIVALI University

BSc in Computer Engineering
June 2011

Skills

Programming Languages
Infrastructure & DevOps
Engineering Practices
  • Event-Driven Architecture & Microservices
  • Infrastructure as Code & CI/CD automation
  • Agile Development (XP, TDD, Scrum, Kanban)
  • Mentoring, Team Enablement & Tech Leadership
  • Open Source Contributions & Product Thinking

Interests

I'm passionate about building systems that last — whether it's a scalable backend, an open-source tool, or a personal project that solves a real need. Outside of engineering, I enjoy reading about personal finance, entrepreneurship, and how people build businesses with code.

In my free time, I experiment with home automation, run a home lab, and occasionally work on indie products. I also love traveling to experience new cultures, and always find time for a good book — usually non-fiction or something that makes me think differently.

Projects

Giox ERP

ERP platform built for Brazilian SMEs fully integrated with e-invoicing (NF-e, NFC-e, MDF-e). Includes frontend, backend in Go/PHP, and full infra automation.

Patrimoniando

Personal finance tracker for multi-currency investments and net worth monitoring. Built solo with Go, MySQL, and NATS. Features include asset tracking, historical charts, and personalized insights - optimized for Expats.

BuildKit SaaS

A SaaS platform to help indie developers rapidly launch products. Focused on reducing boilerplate, simplifying infrastructure, and enabling code-first, solo-friendly workflows.

ML Platform for Deliveroo (UK)

Designed and deployed a machine learning platform on AWS using EKS, ArgoCD, and Terraform. Built internal CLIs to support ML engineers, and initiated a custom network simulator in Go for traffic testing.

SIP Softphone for uTech Tecnologia

Developed a cross-platform VoIP desktop client integrated with the company’s PABX. Built with C++, Qt/QML, JavaScript, and pjsip — supporting Windows, Linux, and macOS.