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Juan Pablo Carzolio

Juan Pablo Carzolio

Benavidez, Buenos Aires Province, Argentina
Member since August 31, 2015
Juan is a versatile and dependable full-stack engineer with ten years of professional experience and a computer science degree. He taught himself programming twenty years ago at the age of eleven. With a strong math and computer science background, he loves to apply reasoning and creativity to understand and solve challenging problems, regardless of the technologies used. He is proficient in several languages, including JavaScript and PHP.
Juan is now available for hire
  • HTML, 12 years
  • Algorithms, 11 years
  • SQL, 10 years
  • CSS, 9 years
  • JavaScript, 8 years
  • MySQL, 7 years
  • PHP, 7 years
  • Amazon Web Services (AWS), 5 years
Benavidez, Buenos Aires Province, Argentina
Preferred Environment
Mac, Ubuntu, Atom, Eclipse, Vim, Tmux, MySQL, Git
The most amazing... I've written is an old-school, "2.5D" raycasting game engine, similar to Doom and Duke3D, written 100% in Java using low-level pixel calculations.
  • Senior Full-stack Developer
    2017 - PRESENT
    Priceline (via Toptal)
    • Worked in an agile team environment, having daily standup meetings, tracking tasks using JIRA, etc.
    • Designed and implemented most of the API-facing and Redux logic of the SPA.
    • Designed and implemented the overall visual structure of the app as well as many of the views and components.
    • Worked together with another front-end developer, reviewing each other's code and discussing important topics together to find the best solutions.
    • Wrote unit tests and test helpers for most major functions and React components, using Jest and Enzyme.
    • Made smaller contributions and suggestions for the app back-end too, written in Java (Spring Boot).
    • Designed the overall app authorization system based on permissions and roles.
    Technologies: React, Redux, JavaScript, ES6, Bootstrap, Webpack, Eslint, yarn, Lodash, Jest, Enzyme
  • Full-stack Web Developer
    2017 - 2017
    Meridix (via Toptal)
    • Migrated a messy old-style PHP codebase to Laravel 5.
    • Redesigned and migrated the UI using Bootstrap, custom CSS, Less, jQuery and "vanilla" JS.
    • Implemented various charts in the dashboard using Chart.js.
    • Fixed bugs and solved migration issues.
    • Rewrote many hardcoded SQL queries using Eloquent and/or parameter binding.
    Technologies: PHP, JavaScript, Laravel 5, Bootstrap 3, Less, jQuery, Chart.js, Redis
  • Architect and Lead Developer
    2016 - 2017
    Vistrata (via Toptal)
    • Took over an existing base project, which I improved and extended.
    • Designed and Implemented a lightweight data access layer to replace a slow custom ORM layer.
    • Designed and implemented a JavaScript component to efficiently render Gantt-like bars from input row data of unlimited size.
    • Implemented Ag-Grid throughout the app to display grids, using custom code to integrate with my Gantt component, add unsupported features, etc.
    • Designed and implemented a technique to batch CRUD operations on the front-end and process them asynchronously on the back-end, allowing for seamless editing with autosave (Google Docs style) and enabling offline editing.
    • Designed the basics of an advanced data revision control system to be implemented in the DB, which is efficient in both space and time.
    Technologies: JavaScript, Ag-Grid, Gulp, PHP, MySQL, REST, JSON, Vagrant, AWS
  • Developer
    2015 - 2016
    CertaPet (via Toptal)
    • Worked with the founders to design and build a platform MVP that would allow their existing business concept to scale.
    • Suggested a split architecture consisting of a PHP back-end with a REST API and a SPA front-end.
    • Designed the DB schema and implemented all of the back-end and API, working together with a front-end developer that got hired later.
    • Integrated Stripe payments trying out different flows, including "auth and capture."
    • Integrated several other third-party services, including Mandrill, Wufoo, WebMerge, and HelloSign.
    • Designed and built the back-end infrastructure in AWS, using RDS, EC2, S3, and IAM.
    Technologies: PHP, MySQL, SQL, REST, JSON, Stripe, Mandrill, Wufoo, WebMerge, HelloSign, AWS, Trello, JIRA
  • Freelance Software Developer
    2011 - 2015
    6v Soft
    • Joined and led a small remote team that worked on feature development, maintenance, bug fixes, optimization, and testing of a high-traffic (2M+ DAU) application on the Facebook platform.
    • Helped maintain, optimize, and migrate the app’s cloud infrastructure based on AWS and Rightscale, including load balancing (ELB), web server arrays, Memcached servers, Cron servers, RDS, S3, Route53, and CloudFront.
    • Developed for an advanced in-house statistics system that allowed real-time monitoring of various traffic metrics.
    • Led the development of mobile web and hybrid (Cordova) versions of the application.
    • Performed A/B testing and experiments to guide feature and design decisions.
    Technologies: PHP, HTML, CSS, JavaScript, Facebook API, Memcached, MySQL, Apache, AWS, PhoneGap
  • Freelance Web Developer
    2007 - 2014
    Estudio F
    • Developed small and medium websites using HTML, JavaScript, PHP, and Flash.
    • Acquired knowledge of and experience in base web technologies.
    Technologies: HTML, JavaScript, PHP, Flash/ActionScript
  • App Developer/Owner
    2009 - 2011
    • Owned and developed several applications on the Facebook platform (including two games) reaching a total traffic of 70k DAU (daily active users) at their peak.
    • Developed an ad network mixing system that maximized revenue by optimizing each network’s traffic share based on their performance (eCPM).
    • Developed a custom analytics system to track app signals (events) based on users’ countries, languages, genders and dates, allowing for A/B testing of certain features and UI choices.
    • Developed the front-end using HTML, CSS, JavaScript, and ActionScript/Flash, the back-end with PHP, Facebook API, and MySQL, and configured Apache on CentOS and Amazon Linux servers.
    • Created and edited all original and derived artwork with Photoshop.
    Technologies: PHP, HTML, CSS, JavaScript, ActionScript/Flash, Facebook API, MySQL, Apache
  • Developer
    2008 - 2009
    • Designed and implemented a system to transfer large files over HTTP from within web applications, with advanced features like pause, resumption, and recovery of uploads and downloads.
    • Designed and implemented a system to transcode media files (images and video) for client applications that featured media previews.
    • Gained deeper understanding and experience in the JavaScript language.
    • Wrote standalone documentation for systems I built.
    • Gained experience in Java web development, learning various frameworks and tools along the process.
    Technologies: Java, Applets, Servlets, Spring, Hibernate, Maven, HTML, CSS, JavaScript, PHP, Apache, Tomcat, Oracle
  • Developer
    2006 - 2006
    • Designed and implemented an algorithm for classroom assignment based in heuristics.
    • Implemented a reservation service and DAO within a Hibernate/Spring architecture.
    Technologies: Java, Spring, Hibernate, Maven, Tomcat
  • MegaSlots (Development)

    A themed "artisanal" slot machine game I built from scratch, implemented as an app for the Facebook platform. It features a rich front-end written both in ActionScript and JavaScript, and a PHP/MySQL back-end. It reached 5k daily users.

  • Solitarium 35 (Development)

    A card solitaire game I built from scratch, implemented as an app for the Facebook platform. It features a rich front-end written mainly in ActionScript, and a PHP/MySQL back-end.

  • Blog (Other amazing things)

    My personal website and blog. You can find a portfolio section there, as well my CV.

  • A Guide to Consistent Hashing (Publication)
    Consistent Hashing is a distributed hashing scheme that operates independently of the number of servers or objects in a distributed hash table. It powers many high-traffic dynamic websites and web applications. In this tutorial, Toptal Freelance Software Engineer Juan Pablo Carzolio will walk us through what it is and how hashing, distributed hashing and consistent hashing work.
  • Languages
    JavaScript, PHP, ECMAScript (ES6), CSS, HTML, HTML5, CSS3, Java, C, SQL, Visual Basic 6 (VB6), Google Apps Script, Lisp, ActionScript 2, Assembly, Sass, Perl, Less, Pug (formerly Jade)
  • Frameworks
    Bootstrap, Jest, React-Bootstrap, Redux, Eloquent, Bootstrap 3, Lumen, Laravel 5, Laravel, PHPUnit, PhoneGap, Swing
  • Libraries/APIs
    jQuery, React Router, React, Ag-Grid, Stripe API, Facebook API, HTML5 Canvas, Mandrill API, Wufoo API, Charts.js, jQuery UI, Java 2D
  • Tools
    Amazon CloudFront CDN, Adobe Photoshop, Atom, Vim Text Editor, Cron, Microsoft Excel, Git, Eclipse IDE, Apache, Xdebug, Firebug, Vagrant, Gulp.js, JIRA, LaTeX, Maven, Redux Thunk, Webpack, Subversion (SVN), Basecamp, Apache Tomcat, Trello, Composer, DataTables, FlashDevelop, Wireshark
  • Paradigms
    Functional Programming, Prototype-based OOP, Imperative programming, Object-oriented Programming (OOP), REST, Agile Software Development, Concurrent Programming
  • Platforms
    Amazon Web Services (AWS), CentOS 6, Linux, AWS EC2, Ubuntu, PDF.js, WordPress, Oracle
  • Storage
    RDS, AWS S3, MySQL, JSON, AWS RDS, Memcached, PostgreSQL, NoSQL
  • Other
    Enzyme, Data Structures, Algorithms, HTTP, AJAX, Image Processing, HTTPS, Multithreading, Computer Graphics, Cryptography, Applets, WordPress Plugins, Blade, TCP/IP, Mobile Web, Audio, AI Programming, Unix Shell Scripting, Genetic algorithms, Neural Networks, PHP/Java Bridge, HTML Email
  • Engineer's degree in Computer Science
    2003 - 2007
    Instituto Tecnológico de Buenos Aires (ITBA) - Buenos Aires
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