David Marín
Verified Expert in Engineering
Software Developer
Cobeña, Spain
Toptal member since July 2, 2015
David is an open-source and open-data enthusiast with more than 23 years of experience as a professional developer. He has acquired various skills, including web programming (PHP and JavaScript), C, C++ (under Linux and Windows), and systems management. Of these skills, David specializes in web programming and has full-stack experience with Symfony PHP-based back ends, jQuery front ends, and WordPress/WooCommerce-based sites.
Portfolio
Experience
- PHP - 20 years
- MySQL - 15 years
- JavaScript - 12 years
- jQuery - 6 years
- WordPress - 5 years
- Symfony - 4 years
- HTML5 - 4 years
- WooCommerce - 3 years
Availability
Preferred Environment
JavaScript, Linux, Symfony, LAMP, PHP, WooCommerce, WordPress, European Union (EU), VAT Return Preparation
The most amazing...
...algorithm I've developed is the control system for the automatic ventilation in Madrid Calle-30, a network of more than 40km of urban tunnels.
Work Experience
Freelance Back-end Specialist
Dark House Development
- Worked on the back-end side for several web projects where I linked several services using their APIs, including Salesforce and Zapier.
- Fixed several problems with WooCommerce Subscriptions.
- Implemented custom plugins for several projects, mainly based on the back end.
Pro-bono System Manager | Web Developer
Fundación MAIOR
- Managed a network of five Windows computers and a Linux file and mail server remotely.
- Developed and deployed www.maior.es using WordPress and WooCommerce.
- Developed and deployed www.amaysirve.es using WordPress and developed a template from scratch using Twig and Timber plugin.
Web Lead Developer
The Healthy Mummy
- Developed multiple custom features for the company website based on WordPress and WooCommerce.
- Cleaned and optimized legacy source code to adapt it to the usage of good practices.
- Developed multiple patches and improvements for several existing WordPress and WooCommerce plugins.
- Implemented an automated test suite with Selenium to track the working conditions of the site.
- Debugged and supported a variety of hosting problems.
- Led a team of three developers working on the site's front and back ends.
- Contributed to VWO tests to improve site conversions.
- Led the effort to carry out the needed adaptations to migrate the sites from PHP 5 to PHP 7 and from PHP 7 to PHP 8.1.
- Adapted all customizations to use the new WooCommerce High-Performance Order Storage (HPOS) database schema.
Web Developer and System Administrator
Navigate Oceania
- Fixed problems in a multi-domain site where the content should be replicated on all the sites.
- Fixed a hacked WordPress installation and improved the site security.
- Added space for advertisements on all the site pages.
- Fixed problems with the translation plugin on the site.
- Updated and cleaned up the plugins used on the site, as many of them weren't needed.
- Migrated several sites from PHP 5 to PHP 7, and later from PHP 7 to PHP 8, and made the needed adaptations.
Freelance Website Developer
Punch Buggy
- Built a custom WooCommerce plugin to connect one site against the AmWin stock management system for a motorbike-shop site.
- Used the WooCommmerce Composite Products plugin and built a customized system to build lures from many pieces. The interface included a preview of the generated lure based on the user's selections. This was for a fishing-apparel shop eCommerce site.
- Built a system to manage shipments from scratch for an important furniture marketplace site built using CraftCMS, using Shippit to centralize shipments. The system calculated exact costs and estimated shipment durations.
- Created the back end used by vendors to totally manage their part orders for a marketplace site.
- Implemented several pages on the CraftCMS site, following mockups provided by the designer.
Woocommerce Developer | Payment Gateway Specialist
Belfort Design Agency
- Developed from scratch a new payment gateway for WooCommerce to receive payments using Stripe Wire Transfer API.
- Enabled the plugin orders as fully paid once the corresponding payments were received correctly.
- Assisted with the site launch and fixed some problems related to the theme and general WordPress/WooCommerce configurations.
Developer
Waterin Whole Limited dba Our Natural Environment
- Developed a PDF Generator system that transforms a crafted HTML document into PDF format using wkhtmltopdf.
- Enabled the system to retrieve the data for the different documents using calls to an existing API through Libcurl.
- Implemented the system as a web service in PHP 7.
Web Developer
Adapt Marketing
- Corrected several problems using WordPress API due to an attack on the server.
- Set up a web page using WordPress and WooCommerce, including selecting and adding plugins and generating custom plugins for specific features.
- Migrated Photoshop designs to HTML/CSS using a newly developed WordPress theme.
Web Developer
Meridix Creative, Inc.
- Modified a website so it now uses Stripe payment gateway instead of PayPal's Payflow API.
- Altered the style of several pages on the website.
- Detected several security-related issues and started tasks to solve them.
Web Developer
Forelock
- Adapted the site to use the Braintree payment gateway.
- Worked on security clean-up for the whole site, removing several security issues as potential SQL injection points.
- Developed new features involving back-end and front-end modifications.
- Worked on a different project, implementing a PHP-based API server to be consumed by the JumpOff mobile app.
Software Developer | System Manager
SICE
- Led a team of four to develop and deploy a proprietary reporting system for Canal de Isabel II, Madrid's public drinking water supplier.
- Managed a three-person team to develop and deploy SICE Nautilus, a web-based operational assistance system that includes incident support and fleet, inventory, and maintenance management.
- Optimized queries and made back-end improvements for a web-based report system for SICE's ITS solution. The improvements allowed the generation and exporting of reports involving huge quantities of data to PDF or Excel.
- Worked on the water control system for the Segura Basin. Analyzed, designed, and implemented new features for the Basin Control Center, including interfacing with an automatic telephone service, C++, Aspen InfoPlus.21, SCADA, and an Oracle database.
- Analyzed, designed, and implemented an automated calculation system using Java and ANTLR tool and other Java modules for the back end of a SCADA system for the auscultation of a dam against a MySQL DB. Deployed in Ebro Basin and dams control systems.
- Developed new features for the Basin Control Center of the Tagus Basin. Deployed the new communication system and network of over 200 embedded x86-based Linux remote units. Built remote administration and updated features for these remote units.
- Created automatic ventilation algorithms for the tunnel control system of Madrid Calle-30. Worked on RCU remote control systems, focusing on ventilation and fire detection subsystems.
- Developed features aimed at improving the scalability and robustness of the remote control unit to support a larger number of I/O signals and connections (C++ for embedded Linux system using x86 arch). This was for the In Madrid Calle 30 project.
- Deployed and managed internal Linux and Windows servers (CVS, SVN, Git) for the development department.
Web Developer and Technical Consultant
Miguel Buckenmeyer & Co.
- Created, installed, and managed several WordPress sites.
- Integrated a web-based file manager in a PHP custom site and helped solve problems in it due to using Java-based plugins.
- Provided technical assistance for different projects.
- Customized an advanced WordPress template, implementing a grid design for the articles.
- Tweaked a PHP-based website for a Spanish perfume company, solving some problems and programming some new features.
Manager of Version Control Systems | C++ Developer
Entelgy
- Led the integration management effort for all Movistar prepayment projects (Spain and Latin America) and the administration of several Linux and Solaris CVS servers.
- Contributed to the implementation of new features for the Movistar Spain prepayment project. This involved C++ multi-architecture development and an extensive use of C++ templates.
- Managed configuration integration systems and servers for the project.
Web Developer | Project Leader | Systems | Database Manager.
Desarrollo y Recursos
- Contributed to the administration, automation, and modernization of web (Apache+MySQL+PHP) and mail servers (Sendmail + Dovecot). Helped define policies for security, configuration management, development, and backups.
- Developed a custom workflow and file management system for San Carlos Clinic Hospital (Madrid, Spain) using PHP for web programming and FDF for printable/electronic forms.
- Designed and implemented an online showcase for Diputación de Jaén.
- Analyzed, designed, and implemented customized services for www.iea.es.
- Worked on the analysis, design, and implementation of a service for getting optimal routes between museums.
Co-owner | System Manager | Software Developer
Advanced Software Production Line
- Helped install, manage, support, and boost security in Debian GNU/Linux servers and firewalls for small and medium enterprise environments.
- Managed projects and analyzed, designed, and implemented AF-Architecture, a multi-tier modular architecture for enterprise software development under GPL open license. The project web page was programmed using a PHP-based app, TYPO3.
- Analyzed, designed, and implemented a CMS system for the firm web page (www.aspl.es) using PHP.
Experience
The Healthy Mummy Websites
http://www.healthymummy.comI started the project cleaning and optimizing lots of legacy code that made the page slow, setting the usage of good practices. We achieved the speed targets.
I also developed multiple custom features to comply with marketing team requirements and multiple patches and improvements for WordPress core and several existing WordPress and WooCommerce plugins.
I developed several custom reports, implemented using low-level complex SQL queries.
I implemented an automated test suite with Selenium to track the working conditions of the site.
I debugged and supported a variety of hosting problems, successfully identifying several bottlenecks in the code.
I led the effort to carry out the needed adaptations to migrate the sites from PHP 5 to PHP 7 and then to PHP 8.1
I adapted the whole set of customizations to use the new WooCommerce HPOS database schema (High-Performance Order Storage).
I successfully migrated the site among several hosting platforms with minimum downtime.
1Place
http://www.1place.com.auI also developed the back end for vendors for this site so that they can keep track of orders and past orders. They can also manage the corresponding shipments, sending the corresponding e-mail messages to final customers.
Ama y Sirve
https://www.amaysirve.esLinux Audit and Monitoring System
Hyperbaric Store
https://hyperbaricstore.comI built a new theme translating Photoshop mockups into the corresponding HTML, CSS, and JavaScript routines.
Reporting System for Canal de Isabel II
https://www.sice.com/en/relevant-projects/real-time-monitoring-of-the-quality-of-water-entering-and-leaving-42-wwtps-minerva-project-phase-ii/I used C#, ASP.NET, the MVC framework, NHibernate, and Microsoft Excel for the back end. For the front end, I used a single Sage application with React and Bootstrap.
Nautilus: Web-based Operational Assistance System
SIDERA Reports: Web-based Reporting System for SICE's ITS Solution
https://www.sice.com/en/sidera-its-tunnels-2/Fundación MAIOR Website
http://www.maior.esTo keep some information, I made adaptations and customizations of a purchased theme and several custom post types.
GnoMint: Open-source Tool for the Management of an X.509 Certification Authority
https://github.com/davefx/gnomintGnoMint is a tool for easily creating and managing certification authorities. It provides fancy visualization of all the information pertaining to a CA, such as x509 certificates, CSRs, and CRLs. GnoMint is currently capable of managing a CA that emits certificates that can authenticate people or machines in VPNs (IPSec or other protocols), secure HTTP communications with SSL/TLS, authenticate and cipher HTTP communications through Web-client certificates, and sign or crypt email messages. It's programmed in C using GTK+, SQLite, and GnuTLS libraries.
The project was created as the final-year project of my master's degree in computer science engineering.
Kelly Doe Studio Website
Calculation Engine for Damdata: Dam Auscultation SCADA
https://www.ofiteco.com/lineas-de-negocio/presas-embalses/aplicacion-damdataMadrid Calle-30 Urban Tunnels
https://www.sice.com/en/relevant-projects/madrid-calle-30-3/I also worked on improving the scalability and robustness of SICE's RCUs (Linux-embedded systems based on x86 architecture) so that they could manage and control more than 9,000 analog and digital inputs and outputs.
Employee Portal for Hospital Clínico San Carlos (Madrid)
I used PHP and MySQL in the server and PDF and FDF for the forms.
Routing Calculator for Huexpo.net
Education
Master's Degree in Computer Science
Universidad Politécnica de Madrid - Madrid, Spain
Certifications
Software Security
The University of Maryland via Coursera
Skills
Libraries/APIs
WooCommerce API, WordPress API, REST APIs, jQuery DataTables, Braintree API, Doctrine, jQuery UI, jQuery, React, Stripe API, Stripe, X (formerly Twitter) API, OpenStreetMap API, Leaflet, WordPress REST API, Highcharts, Infusionsoft API, Libcurl, LibC, GLib, OpenSSL, Stripe Connect, Salesforce API
Tools
ACF PRO, Advanced Custom Fields (ACF), Subversion (SVN), CVS, AffiliateWP, Stripe Checkout, GitHub, Bitbucket, GTK+, Exim4, Apache, DataTables, Redmine, Braintree SDK, wkhtmltopdf, Sendmail, Handsontable, Git, Bower, SoapUI, Nagios, ANTLR, Turbo Pascal, Composer, Microsoft Visual Studio, Google Analytics, Infusionsoft, AWS ELB, Amazon ElastiCache, Metorik, Figma, GTK, Zapier, Amazon CloudFront CDN
Languages
PHP 5, HTML, PHP, C, HTML5, JavaScript, CSS, PHP 7, C++, CSS3, Bash, Bash Script, SQL, Visual Basic 6 (VB6), C#, Java, Assembler, Modula-2
Frameworks
Symfony 2, Symfony, .NET, BEEP, ASP.NET MVC, Selenium, Bootstrap 3, ASP.NET MVC 4, NHibernate
Platforms
WooCommerce, WordPress, Debian Linux, Linux, Ubuntu, LAMP, Web, Marketo, Debian, Azure, Docker, Embedded Linux, Android, Oracle, Windows, Amazon Web Services (AWS), Amazon EC2, VWO, WordPress Theme Design, Klaviyo, Linux RHEL/CentOS, Craft CMS, Drupal, Google Cloud Platform (GCP)
Storage
WP Engine, JSON, MariaDB, PostgreSQL, MySQL, MySQL Server, Databases, Microsoft SQL Server, Amazon S3 (AWS S3), Database Security, Redis, SQL Performance, WooCommerce Database
Paradigms
Model View Controller (MVC), Web Architecture, Web Performance Optimization (WPO), Hosting, Unit Testing, Responsive Layout, Responsive, Search Engine Optimization (SEO), Conversion Rate Optimization (CRO), Security Software Development, Compiler Design, Concurrent Programming, Agile Software Development, Mobile Development, Responsive Web Design (RWD)
Other
APIs, Web Hosting, Web Hosting & Domain Setup, Domains & Hosting, Local Hosting, Embedded Software, Unix Shell Scripting, gnoMint, WordPress Plugins, WooCommerce Subscriptions 2, eCommerce, Architecture, BrainTree, Content Management Systems (CMS), WordPress Themes, Full-stack Development, Integration, Web Development, API Integration, Software Architecture, Payment Processing, European Union (EU), Online Payments, Legacy Code, Legacy Software, CAPTCHA, Ajax, GNU, TCP/IP, X.509, SOAP, Client-server Model, User Interface (UI), Payment APIs, Payment Gateways, Technical Leadership, Technical Reports, Query Composition, Query Optimization, Linux Server Administration, Stripe Payments, WordPress Design, Back-end Development, Back-end, Marketplaces, Cloudflare, Affiliate Marketing, User Experience (UX), Technical Architecture, Data Engineering, VAT Return Preparation, Load Time, Performance, Website Performance, CTO, Email, Code Review, Infoplus WMS, SCADA, Dovecot, Image Manipulation, Embedded Systems, Linux Kernel Drivers, IT Security, Security, Payment Security, Shops, Search, Responsive Design, Responsive UI, Email Marketing, Email Marketing Automation, Google SEO, Organic SEO, SEO Tools, Data Visualization, Regular Expressions, Front-end, Front-end Development, Web Security, Programming, Compilers, Software Engineering, Distributed Software, Operating Systems, Microprocessors, Cryptography, Expert Systems, Networking, IP Networks, Internet Protocols, PayPal, PDF, Reports, SSL Certificates, X.509 Certificates, GnuTLS, RTLinux, Supervisory Control & Data Acquisition (SCADA), Document Management Systems (DMS), Employee Benefits, Dokan, Commerce, Amazon RDS, PHP Performance, Shippit, Leadership, Stripe Subscriptions, Client Portals, Dashboard Design, Stripe Marketplace, WordPress LMS, Learning Management Systems (LMS), Content Delivery Networks (CDN), Technical Writing, Pixel Perfect, Site Speed Optimization, WCAG
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