João Carlos Procópio Florêncio, Developer in São Paulo - State of São Paulo, Brazil
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João Carlos Procópio Florêncio

Verified Expert  in Engineering

Full-stack Developer

São Paulo - State of São Paulo, Brazil
Toptal Member Since
November 29, 2019

João is an entrepreneur with an MSc in computer science (machine learning) from the Universidade Federal de Pernambuco. Along with acquiring a certification in business administration from Insper, João has over ten years of demonstrable experience in successfully leading teams with the Agile methodology, software development, operational research, and co-founding bzTEX.


ASP.NET Core, Firebase, Docker, Socket.IO, WebRTC, Amazon S3 (AWS S3), Node.js...
ARRA Group
JavaScript, JSON API, JSON, Webhooks, Automation, APIs, Segment, PostgreSQL...
JavaScript, API Development, DevOps, Data Science, Full-stack, Data Engineering...




Preferred Environment

Amazon Web Services (AWS), Visual Studio Code (VS Code), Azure, Visual Studio, Linux, Windows

The most amazing...

...project I've developed was a unique algorithm for a vehicle routing problem—an NP complete problem—achieving 10% savings with fleet expenditure.

Work Experience

Software Engineer

2019 - PRESENT
  • Integrated a system via a RESTful API using OAuth 2 authentication.
  • Developed a system to manage small business appointments using React Native for the front end, calendar API integration, and client notifications via WhatsApp to send reminders about appointments. The back-end API was developed with GraphQL.
  • Programmed scalable and secure APIs using JWT authentication and following best practices for RESTful patterns.
  • Created Texas Tea Trader using React, Material UI, and Webpack for configuring the building process in the front end. Used a .NET Core, SQL Server in the back end, and RDS, EC2, S3, and CloudFront from AWS for the hosting infrastructure.
  • Built an image processor with Azure Functions for a client so that they could consume it in their application.
Technologies: ASP.NET Core, Firebase, Docker, Socket.IO, WebRTC, Amazon S3 (AWS S3), Node.js, MongoDB, React Native, Amazon Cognito, AWS Lambda, JavaScript, Entity 6, ASP.NET MVC, Google APIs, WhatsApp API, C#, React, .NET, C#.NET, SQL, Amazon Web Services (AWS), .NET Core, Intuit QuickBooks, GraphQL, Startups, React Apollo, Web Applications, Web Crawlers, Architecture, Express.js, Mongoose, CSS, HTML, Expo, Agile, Full-stack, Front-end, NoSQL, APIs, API Development, REST APIs, Serverless, Azure Functions, RabbitMQ, Microsoft SQL Server

Software Engineer

2021 - 2022
ARRA Group
  • Developed integrations between CATS, an applicant tracking system, and HubSpot, a CRM platform, for a healthcare recruiting company. I used Node.js, containerized with Docker, and deployed the project in the Amazon Elastic Container Service.
  • Consumed a webhook to receive real-time data from CATS and update it into HubSpot.
  • Built a data warehouse connecting different sources, such as CATS and HubSpot, with Segment and used a PostgreSQL database to store all the data until it was consumed for analytics. I used JavaScript to program the integration.
Technologies: JavaScript, JSON API, JSON, Webhooks, Automation, APIs, Segment, PostgreSQL, HubSpot,, Amazon Elastic Container Service (Amazon ECS), Node.js

Full-stack Developer

2021 - 2022
  • Developed an algorithm in Python for optimizing work scheduling in Pfizer labs. The service was made available through a web API built with Flask.
  • Created a full-stack decision-support system for schedule optimization and capacity planning projects.
  • Used React, Apollo, EasyPeasy, and a React timeline calendar for the front end.
  • Built the back end using Knex.js, NestJS, and GraphQL. We also used Hasura for the capacity planning project.
  • Utilized Kubernetes, Docker's Compose, ESLint, and Jest for DevOps and coding processes.
Technologies: JavaScript, API Development, DevOps, Data Science, Full-stack, Data Engineering, Node.js, GraphQL, Combinatorial Optimization, NestJS, React, PostgreSQL, Knex.js, React Apollo, Python, Docker Compose, Kubernetes, Hasura, TypeScript 3, TypeScript, Next.js, SQL, Redis Cache, Pytest, Jira, Web Applications, NumPy, Pandas, Flask, Express.js, CSS, HTML, Agile, Front-end, APIs, Neo4j, Jest, GitHub, Docker

Node.js Developer

2021 - 2021
Nissen Developer Services
  • Contributed to features and fixes for Monti APM. The project used Svelte, Meteor, Node.js, and MongoDB and was written in TypeScript.
  • Made front-end and back-end optimizations to process the data faster when it grew to contain millions of records.
  • Discussed requirements and solutions with the product owner to determine the best strategies for evolving the system.
Technologies: JavaScript, Node.js, MongoDB, TypeScript, Svelte, Meteor, Performance

Lead Developer

2021 - 2021
Beyond Financials Consulting SAS
  • Co-wrote a business plan for a wealth management app, focusing on the technical aspects of the planning and assessing the related challenges.
  • Designed the app and applied a high-level perspective to meet business requirements, including user demand and the service-level agreement.
  • Calculated the time needed to deliver the application based on developers' availability and experience and according to the functional and non-functional requirements.
Technologies: Architecture, Requirements Analysis, Web Architecture, API Architecture, Databases, Requirements, Requirements & Specifications, APIs, CTO, Leadership, Advisory, SaaS, Technology Strategy & Architecture

React Native Developer

2021 - 2021
SAVVI Financial
  • Developed a financial app's front end for Android, iOS, and web using React Native with Expo.
  • Made local data persistence using Redux and Rematch.
  • Added the internationalization (i18n) setup to support multiple languages.
Technologies: React Native, JavaScript, HTML5, CSS3, Redux, React, REST APIs, Git, GitHub, React Native for Web, Portuguese-English Translation, Flexbox, GitLab, iOS, Mobile Development, Web Applications, TypeScript, Express.js, CSS, Expo, Agile, Full-stack, Front-end, APIs, API Development, Cross-platform, Mobile App Development

Full-stack Developer

2020 - 2021
Texas Legit
  • Designed and developed the first version of Texas Tea Trader, a system for managing product markups in the oil and gas industry.
  • Developed the front end in JavaScript with React and built a UI based on Material UI components.
  • Built the back end using Microsoft SQL Server, C#, .NET Core, ASP.NET MVC, and Entity Framework Core.
  • Integrated with financial software, including QuickBooks, the LTLC system, and DTN Energy, and used Power BI for displaying analytic views.
Technologies: HTML, Cloud, Full-stack, JavaScript, CSS, Amazon Web Services (AWS), Databases, CSV, CSV Import, CSV Export, CSV File Processing, C#, .NET Core, QuickBooks API, Intuit QuickBooks, React, Entity 6, Entity Framework, SQL, Amazon RDS, Amazon EC2, MUI (Material UI), Microsoft SQL Server

.NET Web Engineer

2020 - 2020
Tulane University
  • Developed a system for Tulane University to integrate companies, faculties, and students. The solution was developed in ASP.NET MVC.
  • Modeled a SQL Server database and connected it with the application using Entity Framework Core.
  • Utilized Sass and Bootstrap UI to deliver styled-components.
Technologies: ASP.NET, ASP.NET MVC, Entity Framework, Bootstrap, .NET, C#, C#.NET, CSS, HTML, Agile, Full-stack, Front-end, APIs, API Development, Entity 6, Microsoft SQL Server

Lead Developer

2020 - 2020
MOC View
  • Designed and developed a fully functional web and mobile app using React and React Native, respectively. This helped candidates improve their interview skills by training via video conference with colleagues, coaches, and experts in the field.
  • Developed and designed the back end using Node.js, Express.js, Mongoose ORM, and the non-relational database MongoDB.
  • Designed an application following high scalability requirements. Built it with JWT authentication, a stateless server, and Docker containers to be managed with load balancers in the AWS ECS cluster environment.
  • Created bidirectional communication using to provide data synchronization in a live interview session.
  • Built a payment method to buy premium subscriptions using Stripe.
  • Created video conference features using WebRTC technology for web and mobile devices.
Technologies: Stripe, WebRTC, Socket.IO, Express.js, MongoDB, Node.js, Docker, Amazon Elastic Container Service (Amazon ECS), React Native, React, JavaScript, Startups, iOS, Mobile Development, Lean Startups, Web Applications, Mongoose, CSS, HTML, Agile, Leadership, Full-stack, Front-end, NoSQL, APIs, API Development, Jitsi, REST APIs, Video Streaming, Mobile Applications, Cross-platform, Database Design, Prototyping, Minimum Viable Product (MVP), Advisory, SaaS, Technology Strategy & Architecture


2017 - 2019
  • Contributed to the planning and execution of a business strategy regarding client support and DevOps.
  • Established a CI/CD process to ensure delivery quality and structure the IT employees' careers.
  • Coordinated the support and development team using Agile principles.
  • Identified and fixed critical bottlenecks in the system, which made it more stable and capable of recovering from adverse failures. Also redesigned the system architecture to meet future growth expectations.
  • Utilized Firebase Cloud Messaging to establish communication between the server and mobile apps and guarantee push notifications delivery.
  • Developed important new system features and redesigned others, focusing on the user experience.
  • Collaborated with developing a RESTful and SOAP API so that third-party systems could connect. The API also contained webhooks for sending notifications.
  • Made a web crawler for accessing the restricted area of a bank system, collecting data and automatically filling out forms, and submitting them. This was done both programmatically and using Selenium.
  • Created the web application using various tools, including AngularJS, ASP.NET Web API, NHibernate, and Ninject.
  • Built a native Android app using Java and Android SDK packages.
Technologies: CTO, API Gateways, AWS Lambda, Amazon S3 (AWS S3), Amazon EC2, Microsoft SQL Server, NHibernate, Redis, AngularJS, ASP.NET MVC, C#, .NET, C#.NET, SQL, Amazon Web Services (AWS), Startups, Redis Cache, Team Leadership, Management, Mobile Development, Lean Startups, Web Applications, Web Crawlers, JavaScript, Architecture, CSS, HTML, Agile, Leadership, Full-stack, Front-end, APIs, API Development, REST APIs, Firebase Cloud Messaging (FCM), Data Scraping, Web Scraping, Selenium, Advisory, Platforms, SaaS, Technology Strategy & Architecture

Senior Full-stack Developer

2017 - 2017
  • Developed a patient's health quality evaluator, considering the employees' habits and disease history.
  • Worked on test automation with PyTest for unit testing and CI/CD with Jenkins.
  • Collaborated on the NoSQL database design using DynamoBD and a medical consultation module containing video conferencing using TokBox.
  • Co-designed and co-developed a serverless application in Python using AWS Lambda, API Gateway, Amazon S3, and DynamoDB.
Technologies: WebRTC, TokBox, Pytest, API Gateways, Amazon DynamoDB, AWS Lambda, JavaScript, Gulp, AngularJS, Python, Serverless, Amazon Web Services (AWS), Startups, Lean Startups, Web Applications, Microservices, CSS, HTML, Agile, Full-stack, Front-end, NoSQL, APIs, API Development, REST APIs

Project Leader

2011 - 2017
  • Developed the routing algorithm applying combinatorial optimization and machine learning techniques, such as genetic algorithms, simulated annealing, Tabu search, and more.
  • Elicited requirements and studied the impact of new features in the production environment.
  • Led the development team and managed the projects using Agile methodologies.
  • Created the UI for the transport management system application using WinForms.
Technologies: Google Maps API, RESTful Development, SOAP, Amazon S3 (AWS S3), Amazon EC2, Machine Learning, MATLAB, Windows Presentation Foundation (WPF), Windows Forms (WinForms), C#, .NET, C#.NET, SQL, Amazon Web Services (AWS), Startups, Team Leadership, Lean Startups, CTO, Architecture, Agile, Leadership, Full-stack, Combinatorial Optimization, ASP.NET MVC, Microsoft SQL Server

MOC View App
MOC View is a React Native app compatible with Android and iOS that helps candidates practice for their job interviews with colleagues, friends, or contracted coaches. It used, video-conference technology, and bidirectional data flow. The first version of the app, as shown in the demo video, was entirely designed and developed by me.

Go.On | FSM System
Go.On is a mobile and web SaaS application to assist companies in the management of their field teams through planning/routing, tracking, and monitoring of planned activities and sending pre-filled forms regarding the activities carried out.

Work Done:
• Developed the BI for extracting and presenting relevant information about the field operation.
• Redesigned all UI experience in the mobile app.
• Improved the software architecture to solve several performance and stability issues that were compromising the software.
• Performed quality assurance and made many other minor improvements.

Technologies: AngularJS, C#, ASP.NET MVC

Ant Savings

Ant Savings is a personal project that I worked on from start to finish. It is a web application that enables a user to manage their own savings.

The app makes possible to separate the money for specific goals, even when the money is distributed in different investment accounts. The user can keep track and designate specific income streams (dividends and interest from various sources) to reach their long-term goals. Most long-term goals are eventually reached with a series of small deposits and this app helps a user to manage that.

Technologies: ASP.NET MVC


UniRay is a rudimentary demonstration of the ray-tracing technique. The scenery and objects are mathematically described in a file passed as a parameter to the system. The system then reads and generates the image following its shapes, transparency level, reflection, diffraction, opacity, and light sources. The model follows the path of the light, interacting with the environment until it reaches the camera. The final result is an image with a high fidelity degree.

To run the demonstration, access "UniRay/bin/Debug" and find the executable "UniRay.exe." You will discover many input files in the same folder with the extension ".sdl." You can open them and note that there is only a simple description, no pixel-to-pixel information. To execute the program, choose one of the files and drag them to the executable. It will automatically generate an image according to the description of the file, and it will save a ".bmp" file in the same folder. It is also possible to generate your own image by changing the file. The objects are described as quadrics.


C#, HTML, C#.NET, JavaScript, HTML5, Python, CSS, SQL, GraphQL, TypeScript, ECMAScript (ES6), Visual Basic .NET (VB.NET), CSS3, Sass, C, Java, Python 3, TypeScript 3


.NET, React Native, ASP.NET MVC, ASP.NET, Entity 6, ASP.NET Core, Express.js, .NET Core, NestJS, Jest, gRPC, Redux, Next.js, Selenium, Windows Presentation Foundation (WPF), NHibernate, AngularJS, Ember.js, Flutter, Flask, Bootstrap, .NET 4, Svelte, MUI (Material UI)


React, Node.js, API Development, Google APIs, Entity Framework, React Native for Web, Socket.IO, Windows Forms (WinForms), Google Maps API, WhatsApp API, Stripe, WebRTC, REST APIs, Flexbox, Vue, NumPy, Pandas, JSON API, QuickBooks API


Agile, RESTful Development, Scrum, Mobile Development, DevOps, Data Science, Management, Microservices Architecture, Microservices, Requirements Analysis, Web Architecture, API Architecture, Automation, Cross-platform, Database Design


Web Crawlers, API Integration, Lean Startups, Startups, Architecture, Computer Science, APIs, Full-stack, Combinatorial Optimization, Front-end, Web Applications, CTO, Business Strategy, Intuit QuickBooks, Analytics, Leadership, Segment, HubSpot, Jitsi, FTP, API Gateways, Machine Learning, SOAP, Load Balancers, Data Engineering, Portuguese-English Translation, Serverless, Team Leadership, Robotics, Cloud Architecture, Requirements, Requirements & Specifications, Webhooks,, Performance, Cloud, CSV, CSV Import, CSV Export, CSV File Processing, Amazon RDS, Video Streaming, Mobile Applications, Prototyping, Minimum Viable Product (MVP), Mobile App Development, Data Scraping, Web Scraping, Advisory, SaaS, Technology Strategy & Architecture, Platforms, Coding


Jira, Expo, Knex.js, React Apollo, Microsoft Access, Microsoft Power BI, Visual Studio, Gulp, Pytest, MATLAB, Amazon Cognito, Amazon Elastic Container Service (Amazon ECS), Mongoose, Mailchimp, Google Analytics, LINQ to SQL, Jenkins, Celery, TokBox, Docker Compose, Git, GitHub, GitLab, Firebase Cloud Messaging (FCM), RabbitMQ


Google Cloud Platform (GCP), AWS Lambda, Android, Amazon Web Services (AWS), iOS, Docker, NopCommerce, Windows, Linux, Amazon EC2, Blockchain, Ethereum, Firebase, Azure, Visual Studio Code (VS Code), Kubernetes, BigBlueButton, Azure Functions, Meteor


Microsoft SQL Server, MongoDB, PostgreSQL, SQL Server 2016, NoSQL, Google Cloud, Redis, MySQL, Amazon S3 (AWS S3), Amazon DynamoDB, Redis Cache, Hasura, Databases, Neo4j, JSON

2017 - 2018

Certificate in Business Administration

Insper - São Paulo, Brazil

2013 - 2015

Master's Degree in Machine Learning

Federal University of Pernambuco - Recife, Brazil

2007 - 2011

Bachelor's Degree in Computer Science

Federal University of Pernambuco - Recife, Brazil


Certified Developer