Lucas is available for hire

Lucas Luan de Melo Pereira

Verified Expert in Engineering

Back-end Engineer and Developer

Timbó - Santa Catarina, Brazil

Toptal member since May 27, 2025

Expertise

Ubuntu Ruby Visual Studio Development Ruby on Rails Git HTML5 GitHub MacOS Back-end Developers Code Review Linux SQL CSS

Bio

Lucas is a senior back-end engineer with 13 years of experience, including 7+ years of specializing in Ruby on Rails. An expert in building scalable systems across healthcare, government, and human resources sectors, he has delivered robust back-end solutions aligned with business goals. Proactive, adaptable, and quick to embrace new technologies, Lucas will be a great addition to any team.

Portfolio

An Online Freelance Agency

Ruby on Rails 5, Slim, Docker, Agile, Scrum, Linux...

Vitat

Ruby on Rails 6, Datadog, GitHub, Git, Docker, jQuery, API Integration...

CastGroup

Ruby on Rails 4, Linux, Oracle, PostgreSQL, Agile, Kanban, Unit Testing, RSpec...

Experience

Ubuntu - 11 years
Git - 10 years
PostgreSQL - 9 years
JavaScript - 8 years
Agile - 7 years
Ruby on Rails (RoR) - 7 years
RSpec - 5 years
Oh My Zsh - 5 years

Preferred Environment

MacOS, Visual Studio Code (VS Code), Windows Subsystem for Linux (WSL), Ubuntu, RubyMine, Oh My Zsh, Ruby on Rails (RoR)

The most amazing...

...thing I've done was implement Elasticsearch to optimize search across the entire site content at the Goiás Prosecutor's Office.

Work Experience

Ruby on Rails Engineer

2024 - PRESENT

An Online Freelance Agency

Conducted discovery and requirements analysis and produced comprehensive technical documentation. Developed new modules to manage system partners and monitor all customer-related transactions within a payment and credit card platform.
Created custom web applications and automated processes via third-party API integrations, e.g, Glic Payment API.
Coordinated development tasks to ensure timely, budget-conscious delivery.
Implemented data reporting and export functionalities, supporting formats including CSV, TXT, and PDF.
Reviewed filters and refactored N+1 queries to enhance system query performance on Oracle and PostgreSQL databases. Designed database table structures in both Oracle and PostgreSQL to support ongoing activities.
Maintained internal Ruby gems that emulated a microservices architecture as part of a legacy design adopted before my arrival, supporting affiliate data updates and internal system workflows.
Executed on-the-fly script adjustments to resolve real-time issues, reducing customer disruption.
Gained proficiency in using the Slim framework to create forms consistent with system standards.
Contributed to the migration of a legacy Ruby on Rails application from version 4 to 5 and focused on affiliate management, data handling, and payment processing.

Technologies: Ruby on Rails 5, Slim, Docker, Agile, Scrum, Linux, Windows Subsystem for Linux (WSL), Oracle, Ruby on Rails (RoR), RSpec, Git, API Integration, Microservices Architecture, Software Architecture, Kanban, PostgreSQL, Ruby, HTML5, HTML, Code Refactoring, Code Review, Teamwork, Jira, Ubuntu, Clean Code, Programming Languages, APIs, jQuery, Testing, Object-oriented Programming (OOP), CSS3

Senior Ruby on Rails Engineer

2022 - 2024

Vitat

Collaborated with a multidisciplinary team on a healthcare BFF back end in Ruby on Rails for a Flutter app, focusing on knowledge sharing with junior and mid-level peers, developing improvements, maintenance, and scripts.
Participated in implementing WhatsApp API integration to send scheduled water-drinking reminders via Sidekiq, incorporated into a gamification system with interaction history tracking to boost user engagement throughout the day.
Translated business rules into Ruby on Rails code for new plan models and freemium user rules, and developed admin area features to enable administrators to manage plans and user settings effectively.
Collaborated with the team on implementing feature flags using Flipper in the project, enabling controlled feature rollout and improved deployment flexibility.
Led data modeling, entity design, and refactoring for critical features. Employed TDD with RSpec and maintained detailed documentation to ensure scalable, maintainable code focused on improving customer retention metrics.
Contributed to developing a dynamic scoring form in Ruby on Rails, including data modeling and implementation, initially for calculating a health score with potential expansion to other app areas.
Participated in an internal Ruby on Rails chapter, maintaining meeting minutes, proposing improvements, and sharing updates on the Rails ecosystem to foster knowledge and best practices within the technical team.

Technologies: Ruby on Rails 6, Datadog, GitHub, Git, Docker, jQuery, API Integration, Ruby on Rails 7, Team Mentoring, Ruby on Rails (RoR), RSpec, Code Refactoring, Sidekiq, Flipper, Feature Flag, PostgreSQL, Code Review, Data Modeling, Test-driven Development (TDD), Unit Testing, Postman, Clean Code, Clean Architecture, Software Architecture, Programming Languages, APIs, Agile, Scrum, Kanban, Testing, Object-oriented Programming (OOP), CSS3, HTML, Ruby

System Analyst

2021 - 2022

CastGroup

Integrated a guided tour feature built with JavaScript into the new Public Prosecutor's Office of Goiás news portal, enhancing user engagement and accessibility.
Led the redesign of the transparency portal using modern CSS3, HTML5, and jQuery. Updated color schemes, refined UI components, and enhanced accessibility, modernizing the portal to deliver a more intuitive, functional, and inclusive user experience.
Developed the Acts and Norms page with Elasticsearch, enabling advanced search capabilities and better data retrieval.
Implemented Elasticsearch-based content search across the portal, significantly enhancing search performance and accuracy.
Designed and implemented new transparency reports in compliance with federal and state regulations, leveraging Oracle databases with stored procedures and PostgreSQL views to ensure accurate, up-to-date, and reliable data reporting.
Performed in-depth analysis of a legacy Delphi codebase to understand and extract business rules, enabling accurate replication and reimplementation of functionalities in a new Ruby on Rails system.

Technologies: Ruby on Rails 4, Linux, Oracle, PostgreSQL, Agile, Kanban, Unit Testing, RSpec, Elasticsearch, JavaScript, Ruby on Rails (RoR), Git, Jira, Code Review, Refactoring, Clean Code, Back-end Development, Ruby, Code Refactoring, GitLab, SQL, HTML, CSS3, Trello, Software Architecture, Programming Languages, Scrum, Testing, Object-oriented Programming (OOP)

C# Back-end Developer

2019 - 2021

Benner Sistemas

Maintained and enhanced Timecard and Time Bank modules of a human resources system using Delphi and C#. Improved features, fixed bugs, and optimized performance to ensure accurate time tracking and efficient workforce management.
Implemented enhancements in occupational health management for a human resources system using C#, including new forms and workflows as requested by product owners to improve data handling and process efficiency.
Improved managerial functions and the employee onboarding process for an HR system built with C# and Python scripts.
Focused on Agile methodologies, strongly emphasizing bug fixes, continuous improvements, and optimizing system efficiency and functionality.

Technologies: Scrum, C#, Code Refactoring, Testing, JavaScript, Delphi, Code Review, Git, Python Script, Agile, Kanban, Jira, Programming Languages, Object-oriented Programming (OOP), Python

Mid-level Ruby on Rails Back-end Developer

2018 - 2019

Velow

Enhanced and optimized Elasticsearch queries to meet client needs, significantly improving search accuracy and performance in an automotive parts catalog.
Developed a robust Ruby on Rails API for a factory floor app, streamlining real-time operations. Implemented webhooks for safety incident logging and led retrieval from RD Station.
Maintained a Ruby on Rails and Angular eCommerce platform for eSIM sales across airports in Latin America, ensuring stability, implementing updates, and supporting continuous improvements in performance and user experience.
Created the Ruby on Rails API for an app to integrate searches between clients and service providers, based on proximity radius and professional ratings or popularity.
Worked on a Ruby on Rails project to integrate and process global football match data for a mobile app. Developed core features before the client discontinued the project.

Technologies: Ruby on Rails 6, Ruby on Rails 5, Linux, Scrumban, Agile, Systems Analysis, Ruby on Rails (RoR), Git, API Integration, Code Review, Clean Code, APIs, Back-end Development, Angular, JavaScript, HTML5, CSS3, Business Systems Analysis, Code Refactoring, RESTFul APIs, REST, RESTful Routes, Programming Languages, Scrum, jQuery, Object-oriented Programming (OOP), HTML, Ruby

C# Developer

2015 - 2017

Ellevo

Served as the first technical point of contact for support, investigating source code to resolve complex issues beyond standard support scope.
Ensured rapid incident resolution to meet SLA targets, coordinating closely with support and engineering teams.
Delivered system improvements using C#, ASP Classic, and ExtJS, including implementing customizable document template generation to enhance user flexibility and efficiency.
Developed PL/SQL reports for the commercial team to integrate client data into Power BI dashboards.

Technologies: C#, Ext JS, Classic ASP, MySQL, Microsoft SQL Server, Vanilla JS, Git, CVS, JavaScript, HTML5, CSS3, Back-end Development, Code Review, PL/SQL, SQL Server 7, Clean Code, OOP Designs, Programming Languages, jQuery, Kanban, Object-oriented Programming (OOP), HTML

Ruby on Rails Developer

2014 - 2015

Gett Tecnologia

Received practical training and mentorship on Ruby on Rails and ExtJS frameworks.
Developed and optimized fiscal and management reports, including performance refactoring and code review.
Initiated the communication and integration project to generate remittance files and print bank slips.
Repaired and enhanced routines for export invoice issuance.
Created new management registration modules to support operational needs.

Technologies: Code Refactoring, Testing, Linux, Object-oriented Programming (OOP), Ruby on Rails 4, Ext JS, CSS3, CSS, HTML, Ruby on Rails (RoR), MacOS, RSpec, Programming Languages, APIs, Scrum, Ruby

Python Developer

2010 - 2013

LZT Soluções em Informática

Maintained and developed new features for management modules, including user registration and access control.
Enhanced import and export routines for invoice management files, improving data accuracy and process efficiency.
Trained in Python programming, Django framework, PostgreSQL database management, and GTK graphical interface library.

Technologies: Python, Django, Linux, PostgreSQL, TortoiseCVS, GTK, Programming Languages, jQuery, Object-oriented Programming (OOP)

Experience

Public Prosecutor's Office of Goiás | Official Portal

As a contracted developer through CastGroup, I modernized the main portal's layout and implemented a guided tour feature designed to enhance user engagement and accessibility. I also developed and integrated advanced content search capabilities, including indexing the entire portal content with Elasticsearch, significantly improving overall search functionality and data retrieval for acts, norms, and other documents.

Link: https://www.mpgo.mp.br/portal/

Public Prosecutor's Office of Goiás | Public Transparency Portal

As a contracted developer through CastGroup, I implemented the overhaul of the Public Transparency Portal. I spearheaded the overhaul, improving its functionality and user experience. I also designed and implemented new transparency reports in compliance with federal and state regulations, ensuring up-to-date and accurate data reporting.

Link: https://www.mpgo.mp.br/transparencia/

Education

2016 - 2022

Bachelor's Degree in Software Engineering

UniCesumar - Maringa, Parana, Brazil

Certifications

NOVEMBER 2023 - PRESENT

Process Flowcharts & Process Mapping - The Beginner's Guide

Udemy

MAY 2020 - PRESENT

Enterprise Design Thinking Practitioner

IBM

SEPTEMBER 2019 - PRESENT

Scrum Fundamentals Certified

SCRUMstudy

Skills

Libraries/APIs

jQuery, Sidekiq

Tools

GitHub, Git, RSpec, RubyMine, Oh My Zsh, TortoiseCVS, GTK, Postman, Jira, GitLab, Trello, CVS

Languages

Ruby, HTML, HTML5, JavaScript, C#, Delphi, CSS3, CSS, Python, SQL, Python Script

Frameworks

Ruby on Rails 5, Ruby on Rails (RoR), Slim, Ruby on Rails 6, Ruby on Rails 4, Ruby on Rails 7, Ext JS, Classic ASP, Vanilla JS, Django, Angular

Platforms

Visual Studio Code (VS Code), Ubuntu, MacOS, Docker, Linux, Oracle

Paradigms

Kanban, Agile, Scrum, Unit Testing, Code Refactoring, Testing, Object-oriented Programming (OOP), Microservices Architecture, Test-driven Development (TDD), Refactoring, Clean Code, Clean Architecture, REST

Storage

Datadog, PostgreSQL, Elasticsearch, MySQL, Microsoft SQL Server, PL/SQL, SQL Server 7

Other

APIs, API Integration, Windows Subsystem for Linux (WSL), Software Engineering, Software Modeling, Software Project Management, Software Architecture, Software QA, Programming Languages, Team Mentoring, Code Review, Scrumban, Systems Analysis, Design, Empathy, Ideation, Business Process Flow Diagrams, Teamwork, Flipper, Feature Flag, Data Modeling, Back-end Development, Business Systems Analysis, RESTFul APIs, RESTful Routes, OOP Designs

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