Sergio Marcelino, Developer in João Pessoa - State of Paraíba, Brazil
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Sergio Marcelino

Verified Expert  in Engineering

Software Developer

João Pessoa - State of Paraíba, Brazil
Toptal Member Since
September 30, 2022

Sergio is an experienced tech and team lead, keen on mentoring junior developers and keeping teammates motivated. He has over a decade of experience in the software industry, specializing in testing tools and methodologies. In one of Sergio's most successful projects, he led the team to deliver a product on the proper schedule with 100% unit test code coverage, 100% feature coverage for end-to-end tests in the API, and 100% coverage with automated browser end-to-end testing.


Node.js, React, Test-driven Development (TDD), Serverless Architecture...
Node.js, Test-driven Development (TDD), React, PostgreSQL, TypeScript, Pulumi...
TypeScript, Serverless Architecture, PostgreSQL, Data Science, Data Analytics...




Preferred Environment

IntelliJ IDEA, MacOS, Chrome

The most amazing...

...thing I've created is a marketplace for Auto Enthusiasts, focusing on automated tests. We had 3% of sprint capacity dedicated to fixing bugs and defects.

Work Experience

Tech Lead and Team Lead

2020 - PRESENT
  • Helped the team communicate with other internal development teams, taking part in architectural meetings and planning meetings with the product management.
  • Brought new technologies and paradigms to our team ahead of time and identified and prioritized technical debts with the product team.
  • Collaborated with back- and front-end developers and SDET specialists, identifying and helping solve emergent problems, thus contributing to the team's success.
  • Built a marketplace with hundreds of thousands of monthly users for a company listed on NYSE that deals with daily VPN, networking, and WAF security scans.
  • Helped with recruitment and finding the right candidates by performing technical and cultural interviews and reviewing code challenges.
Technologies: Node.js, React, Test-driven Development (TDD), Serverless Architecture, Amazon Web Services (AWS), Terraform, Infrastructure as Code (IaC), Playwright, GraphQL, CI/CD Pipelines, Azure DevOps, TypeScript, Amazon DynamoDB, Web Security, Next.js, Contentful, Front-end Development, Headless Software, Amazon S3 (AWS S3), Software Architecture

Founder and Software Engineer

2018 - PRESENT
  • Founded Trackify to facilitate deliveries from local restaurants and grocery stores by linking delivery people, companies, and stores via a mobile app and a cloud dashboard.
  • Developed the dashboard, a real-time application that tracks the couriers and charges and splits the money between the parts.
  • Created the infrastructure using an infrastructure-as-code tool, Pulumi, with a container service using AWS ECS.
Technologies: Node.js, Test-driven Development (TDD), React, PostgreSQL, TypeScript, Pulumi, Infrastructure as Code (IaC), Amazon Web Services (AWS), Flutter, SQL, REST APIs, Next.js, Front-end Development, Amazon S3 (AWS S3)

Senior Full-stack Engineer

2019 - 2020
  • Acted as the principal full-stack engineer on an analytics product that processes millions of orders weekly and generates fast reports on complex queries, boosting marketing performance in several large Shopify stores.
  • Researched the best indexes and best-performing SQL queries to have complex reports from a database with billions of rows in one-digit seconds.
  • Worked on multitenant solutions for dozens of clients, processing millions of Shopify orders daily.
Technologies: TypeScript, Serverless Architecture, PostgreSQL, Data Science, Data Analytics, Kubernetes, React, Test-driven Development (TDD), SQL, REST APIs, Next.js, Front-end Development, Amazon S3 (AWS S3), Web Scraping

Tech Lead and Java Software Engineer

2018 - 2019
  • Acted as the tech lead at the payment team, working on a payment gateway to charge invoices for the company's products.
  • Developed the gateway using a microservices architecture. The gateway enables creating subscriptions, taking some user metrics to generate invoices and charge credit cards, and splitting the cash between multiple accounts.
  • Prepared the application to have 100% unit test code coverage across repositories.
Technologies: Java, Microservices Architecture, PostgreSQL, Test-driven Development (TDD), Angular, Kubernetes, SQL, REST APIs, Front-end Development, Amazon S3 (AWS S3)

Co-founder and Software Engineer

2013 - 2019
Portal Justiça
  • Built the website as a sole developer. The website is still live without issues.
  • Used Node.js with AngularJS and Vue for developing the website and deployed it in AWS.
  • Planned for the website scalability and maintenance. It received over a million page views in one single month.
Technologies: Docker, Vue, Node.js, Test-driven Development (TDD), CI/CD Pipelines, Amazon Web Services (AWS), Linux, SQL, REST APIs, React, Next.js, Front-end Development, Nuxt.js, Headless Software, Amazon S3 (AWS S3), Web Scraping, MySQL, Software Architecture

Lead Software Architect

2012 - 2018
  • Worked on a PCI-compliant transactional server for the payment industry, targeting companies like Banco Itau, Rede, CPFL, and Cielo.
  • Built a marketplace,, using Java, microservices, TDD, AngularJS, and Oracle for SmartPOS so developers could integrate with the payment solution inside POS without needing the PCI.
  • Developed a gateway using Java, Oracle, and SQL Server to manage smart safes.
  • Created a gateway using Java, microservices, TDD, and a React Native and Redux-based app for fidelity programs in the retail industry.
Technologies: JavaScript, React Native, Java, Microservices, PCI, SQL, REST APIs, React, Front-end Development, Software Architecture, Oracle

Marketplace for Auto Enthusiast

Worked on creating a marketplace platform with millions of users. The main technologies used in the project include Node.js, Terraform, AWS, TypeScript, Next.js, React, DevOps, GraphQL, and Playwright for end-to-end tests, and everything is running in Serverless.

This project had several repositories in microservices architecture, with 100% unit test code coverage and 100% feature coverage on end-to-end tests.

As a team lead, I facilitated one-on-one meetings with my teammates to help
them grow in their careers. I also worked with the other leaders to share the teams' concerns so we could address them and always keep the team motivated and fully functional. I've contributed to building other teams helping with onboarding and mentoring for the first three months.

Analytics Platform for Shopify Stores

As a principal full-stack engineer, I've worked on an analytics product to process millions of orders weekly and generate speedy reports on complex queries. It helped boost marketing performance on several large Shopify stores.

The database had to handle billions of records, with millions being ingested daily. It had to build dozens of SQL queries for analytics reports for the clients, all running in single-digit seconds.

Local Deliveries Tracking Platform

Founded and developed Trackify, a real-time application with a cloud dashboard to facilitate deliveries from local restaurants and grocery stores. It connected the delivery people, companies, and stores with a mobile app and a cloud dashboard. The dashboard tracks the couriers and charges and splits the money between the parts.

The tech stack used in the project includes Node.js with TypeScript, PostgreSQL, Serverless Container Service, React, and Flutter.
2007 - 2012

Bachelor's Degree in Computer Science

UNIPE - João Pessoa, PB, Brazil


React, Node.js, REST APIs, Playwright, Vue


Terraform, IntelliJ IDEA


Next.js, Nuxt.js, React Native, Angular, Flutter, Chrome


JavaScript, TypeScript, GraphQL, SQL, Java


Design Patterns, Microservices, Test-driven Development (TDD), Microservices Architecture, Serverless Architecture, Azure DevOps, Data Science


Docker, Linux, Amazon Web Services (AWS), AWS Lambda, Contentful, Kubernetes, MacOS, Oracle


PostgreSQL, Amazon DynamoDB, Amazon S3 (AWS S3), MySQL


Software Engineering, Data Structures, Web Development, CI/CD Pipelines, Infrastructure as Code (IaC), Front-end Development, Headless Software, Web Scraping, Webhooks, Operating Systems, PCI, Pulumi, Data Analytics, Web Security, Software Architecture

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