Sebastian Mateo Horta, Developer in Montevideo, Montevideo Department, Uruguay
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Sebastian Mateo Horta

Verified Expert  in Engineering

Full-stack Developer

Montevideo, Montevideo Department, Uruguay
Toptal Member Since
June 23, 2017

Sebastian is a full-stack web and Android developer with over 17 years of engineering experience. He has worked with many programming languages, frameworks, and technologies, but he specializes in Java Spring Boot and React. Sebastian loves to take on new challenges and deliver beautiful applications.


J2 Global Consensus - Everyday Health Group - Babycenter
Java, Hibernate, Spring Boot, Jakarta Server Pages (JSP), jQuery, MySQL, React...
Hollywood Spill, LLC (via Toptal)
Kotlin, Android, Java, Scrum, RESTful Web Services, Git...
Inpoint (via Toptal)
SQL, REST, Swagger, JUnit, Spring Boot, Java 8, Java, Spring...




Preferred Environment

Git, IntelliJ IDEA, Linux, MacOS

The most amazing...

...project I've developed is a live sound recognition system used to determine the television channel being watched by a mobile app user in real-time.

Work Experience

Senior Full-stack Developer

2017 - PRESENT
J2 Global Consensus - Everyday Health Group - Babycenter
  • Oversaw the maintenance of more than six legacy Babycenter systems built in Java Spring.
  • Migrated Babycenter's legacy systems for its US and international sites into JavaScript technologies such as React, GraphQL, and Next.js.
  • Contributed to resolving critical bugs at large-capacity consumer-facing websites.
Technologies: Java, Hibernate, Spring Boot, Jakarta Server Pages (JSP), jQuery, MySQL, React, GraphQL, Material UI, Apollo, AWS CLI, Redis, React Apollo, PM2, Amazon Web Services (AWS), Next.js, Node.js, Mockito, HTML, Spring, Jira, Docker, XML, NPM, Jenkins, JSON, RESTful Development, Bitbucket, Ajax, Database Modeling, Apache Tiles, Gradle, REST APIs, Redis Cache, TypeScript, AWS Lambda, API Design, Back-end, Web Development, Architecture, Content Management Systems (CMS), Technical Leadership, Solution Architecture, GitHub Actions, APIs, Express.js, Artificial Intelligence (AI), NoSQL, ChatGPT, Python, Firebase, GitHub, Tailwind CSS, API Integration

Android Developer

2018 - 2018
Hollywood Spill, LLC (via Toptal)
  • Implemented an Android app based on an existing iOS app.
  • Implemented an event-driven design based on WebSockets.
  • Fixed the Phoenix WebSockets connection and reconnection in the Android and iOS apps.
  • Learned and adapted new technologies, including Kotlin, Swift, and Python, to meet specific client requirements quickly.
Technologies: Kotlin, Android, Java, Scrum, RESTful Web Services, Git, Agile Software Development, Apache Tomcat, Java 8, Object-oriented Programming (OOP), Object-oriented Design (OOD), IntelliJ IDEA, Jira, Docker, XML, Jenkins, JSON, RESTful Development, Gradle, REST APIs, API Design, Architecture, Technical Leadership, Solution Architecture, Stripe, APIs, Heroku, GitHub, API Integration

Senior Java Developer

2017 - 2018
Inpoint (via Toptal)
  • Led the back-end development for a system that dealt with complex business logic.
  • Created unit tests with more than 90% of code coverage.
  • Helped the project manager by leading the daily meeting calls.
Technologies: SQL, REST, Swagger, JUnit, Spring Boot, Java 8, Java, Spring, REST API Architecture, Scrum, RESTful Web Services, Git, Agile Software Development, Apache Tomcat, Object-oriented Programming (OOP), Object-oriented Design (OOD), IntelliJ IDEA, Apache Maven, Jira, Docker, PostgreSQL, Redux, XML, Jenkins, JSON, RESTful Development, Gradle, REST APIs, API Design, Back-end, Technical Leadership, Solution Architecture, APIs, Firebase, GitHub, API Integration

Software Engineer

2014 - 2017
  • Created a proof-of-concept web application with React for the front end and Spring Boot for the back end, which consumed external REST services.
  • Developed a web application that managed system orders; it was built with Spring and Vaadin for the front end, and the back end consumes external REST services. The front end was built based on some configuration received from REST services.
  • Developed different processing interface modules for merchant clients of Verifone, which were integrated with its Gateway Core developed in Java EE and Netty. Also migrated legacy modules to new modern modules that follow EMV specifications.
  • Refactored a batch system for Verifone that ran once a day to complete some end-of-the-day jobs on transactions batches.
  • Developed a transactional system for a payments gateway that must be able to integrate with multiple clients, manage thousands of transactions per day, and must be PCI compliant. Used Java EE, JMS, WebSockets, JavaScript, SQL, Solr, and JBoss.
  • Applied Scrum Agile methodology for every project and was certified as a Scrum Master by the Scrum Alliance.
Technologies: React, Vaadin, Spring Boot, Spring, Netty, Java EE, Certified ScrumMaster (CSM), Java, JavaScript, SQL, REST API Architecture, CSS, JUnit, Scrum, RESTful Web Services, MySQL, Git, Agile Software Development, Apache Tomcat, Linux, jQuery, Object-oriented Programming (OOP), Object-oriented Design (OOD), IntelliJ IDEA, HTML, Apache Maven, Jira, Docker, PostgreSQL, XML, NPM, JMS, Jenkins, JSON, RESTful Development, Ajax, Database Modeling, WebSockets, WildFly, Mockito, Gradle, Bootstrap 3+, REST APIs, API Design, Back-end, Web Development, Architecture, APIs, GitHub, API Integration

Full-stack Web and Mobile Developer

2009 - 2014
  • Developed mobile home banking web applications to access banking information from a smartphone. Built on the MVC .NET framework and using jQuery, jQuery Mobile, JavaScript, and CSS for the front end.
  • Supported an Android mobile application for viewing horse-racing results and information; I also refactored the app's inner design by adding Android design best practices. This app consumes external REST Services using JSON objects.
  • Created an Android mobile application by migrating an Apache Cordova app that used jQuery Mobile for improving app performance and user experience on smartphones. This app consumes REST Services using JSON objects and OAuth authentication.
  • Developed a Cordova Apache mobile application using the JavaScript library, jQuery Mobile, and CSS (Android and iOS versions). The app was able to recognize live TV programs by recording the TV sound and sending it to a recognition sound system.
  • Architected a back-end system that was able to recognize live TV by recording different TV channels via the mobile application. This used a fast Fourier transform (FFT) algorithm for analyzing and comparing frequencies on little chunks of information.
  • Supported a commercial management system for a public service entity built with Java EE, SQL Server, and PowerBuilder. It was based on a client's legacy architecture.
  • Created a web application for online video courses, which was integrated with a nopCommerce eCommerce shopping cart; it was built with MVC .NET, SQL Server, ActionScript 3.0 for the video player, HTML, and JavaScript.
  • Improved the performance of database triggers and stored procedures of a risk analysis application based on Visual Basic 6 and SQL Server.
  • Created a web application for trying on sunglasses at an optical shop. The application was developed using the Yahoo! User Interface Library, allowing users to upload a photo and virtually try on various sunglasses with their picture.
Technologies: Microsoft SQL Server, ActionScript 3, Visual Basic 6 (VB6), IIS, ASP.NET MVC, Visual Basic .NET (VB.NET), .NET, C#, jQuery Mobile, Cordova, JavaScript, CSS, HTML, Android, Java EE, Java, SQL, REST API Architecture, JUnit, RESTful Web Services, MySQL, Agile Software Development, Apache Tomcat, jQuery, C#.NET, Visual Studio 2012, Object-oriented Programming (OOP), Object-oriented Design (OOD), Jira, XML, JSON, RESTful Development, Bitbucket, Ajax, Database Modeling, Eclipse IDE, IIS 7, Twitter API, Bootstrap 3+, Facebook API, REST APIs, API Design, Back-end, Web Development, Architecture

Web Developer

2006 - 2009
Tata Consultancy Services
  • Supported a full-stack management system for MoneyGram locations based on a service-oriented architecture that interacted with some legacy services, built with Java EE, JUnit, and Swing.
  • Worked with Agile methodologies like Scrum and used best practices with extreme programming, such as test-driven development (TDD) and continuous refactoring.
  • Created an internal human resources application based on Java EE, Struts, HTML, JavaScript, MySQL, and Tomcat.
  • Worked with a process improvement team on a CMMI model.
  • Developed a web application for quoting and processing insurance policies on maritime cargo around the world. Used Java EE, TestNG, Struts, HTML, JavaScript, jQuery, JasperReports, Hibernate, and Oracle 10g.
  • Managed and deployed a web application on maritime cargo insurance policies—worked on developing, testing, and producing servers.
  • Created a testing result interpreter tool based on XML to improve team proficiency.
Technologies: Eclipse, MySQL, Oracle 10g, JavaScript, HTML, Apache Struts, Swing, TestNG, JUnit, Java EE, Java, SQL, REST API Architecture, CSS, Agile Software Development, Object-oriented Programming (OOP), Object-oriented Design (OOD), XML, JSON, RESTful Development, Bitbucket, Ajax, Database Modeling, Eclipse IDE, Kanban, REST APIs

MeLook: Live Video Transmission for a Journalism Investigation Project
MeLook was a social network that was focused on journalism—it allowed anyone with a smartphone to report news through live video streams.

The system consisted of three applications: a mobile application, a web application, and a back-end system for the management and administration of flows. The mobile application was developed for the Android platform.

Three different phases were defined for this investigation: research, product definition, and system construction. The research phase included the technical research for the smartphone streaming live technology. In the product definition phase, a design thinking methodology was used, which made it possible to focus on the user's needs. Finally, the product was built using Scrum as a framework.

This was an investigative project for my software engineering degree.

BabyCenter is the world's number one digital parenting resource, reaching millions of new and expectant parents monthly through our global websites, mobile apps, online communities, email, and social platforms.

I maintained and modernized legacy codebases built on Java and PHP technologies, transforming them into a greenfield project with new codebase technologies, including React, Node.js, Next.js, Apollo, and GraphQL.
2005 - 2014

Bachelor's Degree in Systems Engineering

Universidad ORT Uruguay - Montevideo, Uruguay


Node.js, React, REST APIs, JMS, jQuery, Facebook API, jQuery Mobile, Twitter API, Stripe


IntelliJ IDEA, Git, Apache Tomcat, Bitbucket, Jira, Jenkins, GitHub, Apache Maven, Eclipse IDE, AWS CLI, React Apollo, PM2, Visual Studio 2012, WildFly, NPM, Gradle, ChatGPT


Spring, JUnit, Spring Boot, Mockito, Apache Tiles, Hibernate, Jakarta Server Pages (JSP), Next.js, Spring 5, Redux, TestNG, Material UI, Express.js, Swing, Apache Struts, ASP.NET MVC, Vaadin, Netty, .NET, Bootstrap 3+, Swagger, OAuth 2, Tailwind CSS


Java 8, GraphQL, HTML, Java, CSS, JavaScript, SQL, XML, JavaScript 6, TypeScript, Kotlin, C#, Visual Basic .NET (VB.NET), Visual Basic 6 (VB6), ActionScript 3, C#.NET, Python


REST, REST API Architecture, Agile Software Development, Scrum, Object-oriented Programming (OOP), Object-oriented Design (OOD), RESTful Development, Kanban


Android, MacOS, Java EE, AWS Lambda, Amazon Web Services (AWS), Linux, Heroku, Eclipse, Docker, Firebase


JSON, PostgreSQL, MySQL, Redis, Database Modeling, Redis Cache, Oracle 10g, Microsoft SQL Server, NoSQL


Certified ScrumMaster (CSM), RESTful Web Services, API Design, Back-end, Architecture, Content Management Systems (CMS), Technical Leadership, APIs, API Integration, Ajax, Apollo, Web Development, Solution Architecture, GitHub Actions, IIS, IIS 7, WebSockets, Cordova, Akamai, Machine Learning, Artificial Intelligence (AI)

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