Imej profil ocalderon
Penanda El Salvador Santa Tecla, El Salvador
Ahli semenjak 17 Oktober 2013
2 Cadangan


Dalam Talian Luar Talian
Full Stack Engineer with 10 years of experience overall working in a wider range of industries. My focus and main goal is to bring my clients a unique experience by providing high quality Software Services. I have a strong expertise in building enterprise applications from design to implementation, from A to Z. UI Design? Backend & Frontend development? Iplementation? SysAdmin? I'm an expert on it. I have proven experience in JAVA and Javascript languages. 6 years of experience in JAVA supports me and 4 years working with Javascript frameworks in both Frontend and Backend. ReactJS and all its ecosystem is what i use on my daily basis in order to make user experience unique.
$26 USD/hr
16 ulasan
  • 94%Kerja Diselesai
  • 100%Mengikut Bajet
  • 74%Tepat Pada Masa
  • 40%Kadar Ulang Upah


Ulasan Terkini

  • Imej Fernando Backoffice web admin with react.js controls €544.00 EUR

    “Oscar es una persona, amable, dispuesta y buen profesional. Recomendado.”

  • Imej Pedro L. Crear una aplicación para Android $655.00 USD

    “Great developer! Thanks.”

  • Imej Ricardo T. Project for ocalderon $100.00 USD

    “Gracias Oscar por tu colaboración. Espero que podamos seguir trabajando juntos.”

  • Imej Ricardo T. Write some Software $133.00 USD

    “Gran trabajo y comunicación con Oscar. Seguro tendré más proyectos con el.”

  • Imej Petr S. Web-based editor of structured texts €244.00 EUR

    “Overall I was happy with the quality of the work delivered. I highly appreciated the quality of communication during the project. Oscar was regularly reporting about the progress of the work and asking right questions whenever needed. From technical perspective, I find the implementation in ReactJS+Redux to be up to current standards, with a well readable code and good code organization. Unfortunately the project took more time than originally expected. The reasons were communicated and we decided to continue with the project, but it I imagine it could have become on issue had the project been on a tight schedule.”

  • Imej Price H. Project for ocalderon -- 2 $15.00 USD

    “He worked well for last 2 times. But he has no responsibilities. I gave him big project but not answering for 3 days and did nothing thought deadline is near. I talk to every client. Don't work him again. I'll He has great skill on only React. I gave him java project, but he made wrong result. Very bad. No responsibility.”


JAVA Training 101 – 301

Jun 2014 - Aug 2014 (2 months)

Private JEE training for government employees during 3 months during night, after work hours. Starting from basic JAVA syntax, data types, loops, following to JEE web development using Servlets & JSP and after that, Spring MVC, Spring DI and Spring Security. Finally I taught them JSF development using Mojarra 2.0 and PrimeFaces 5.0, running on Wildfly 8.

Personal spending management App

May 2014 - Jul 2014 (2 months)

An android app about personal spending and incomes management developed for a single user. The app lets you create accounts like pocket, credit card, savings account; and after that register incoming and spending movements that affect one or various accounts. The app also has a wide variety of reports using bar graphs or pie graphs. It was developed using Eclipse Kepler IDE, compatible with Android 14 y 19 and designed for smartphones and tablets (using Fragments).

Point of Sale application for an agro service

Jan 2014 - Apr 2014 (3 months)

In this project I developed some modules but also I managed 3 JAVA developers by assigning requirements and also create the Gantt diagram for Project monitoring and resource management. This application was for an agro service, with Inventory module, Point Of Sale, Invoices and a lot of sales reporting, like sales per branch, sales per product, sales per product categories, earnings based on product sales prices. It has support for manage multiples prices per product according to clients. It was developed using Spring MVC 4.0 and JSP with Velocity with PostgreSQL 9.3 database through Hibernate JPA, running on JBoss AS 7.1 on CentOS 6.5 x64

CRM Backend using EJB and WS

Nov 2013 - Mar 2014 (4 months)

Backend development for supporting a newly CRM system. The frontend was developed with AngularJS and I created the backend. This backend lets you manage potential clients, projects, client activities, opportunities and it’s monitoring, and reports. Developed as Stateless EJB Session Beans using EJB 3.2 available as RESTFUL Web Services. The backend run over JBoss AS 7.1 using PostgreSQL 9.3 database through Hibernate JPA.

PostgreSQL migration from 9.0 to 9.3

Oct 2013 - Nov 2013 (1 month)

PostgreSQL cluster migration from 9.0 to 9.3 in a government institution. It was required to reinstall the OS so they decided to update database server too. The procedure was the generation of compressed backups, copied to a second server through SCP in case of failure or data loss. After OS reinstallation, I proceeded to install PostgreSQL server and tune configuration settings. Once properly installed and tuned, I restored the roles and database and finished with some connection tests and data integrity tests. Operating system was RHEL 5.8 .

CRM Application for a bus station

Apr 2013 - Aug 2013 (4 months)

Project planning, development and implementation of a customized CRM application for a bus station with a lot of commerce’s inside it. This application lets you manage the entire bus terminal in terms of spaces rental for various businesses inside the bus terminal. The CRM part of the application is used to manage ads that are shown in screens inside the buses. You register the opportunities of selling ad time on the screen to potential companies, and you monitor this process inside the application. Developed using CDI with JSF 2.0 and PrimeFaces 4.0, using PostgreSQL 9.3 database through Hibernate JPA, running on JBoss 7.1 .

Crafts management Application for sea shipping government unit

Mar 2013 - Oct 2013 (7 months)

I was in charge of this Project entirely, so I managed a couple of PHP developers and also developed some modules. I had the task of talking with final users to get information, learn about crafts and technical data about it, and to model the screens and also the database diagram. After that I created the Gantt diagram to Schedule Project tasks. This application is used to have a register of each craft in our country, like a car register but for crafts. Categorized based on the craft type, owners, also a register of all crafts owners, documentation or contracts of ownership of craft are uploaded in this application. Developed on PHP, using Codeigniter framework and MySQL database.

Craft arrivals register application

Jul 2012 - Nov 2012 (4 months)

Project planning, development and implementation of a customized web application used to register craft arrivals to El Salvador harbors because, when this happens, the craft owner or driver must meet some documentation requirements. Prior to application’s implementation, it was a mess to handle those papers, but now through the application they upload the documents and after that users only can Access those documents which are for them. Developed on PHP, using Codeigniter framework and MySQL database.

Construction projects management application

Jun 2012 - Mar 2013 (9 months)

Construction projects management application Project planning, tasks scheduling and entire development of a customized enterprise web application in JAVA for a non-profitable organization which build houses for poor people. This application has modules and reports to manage the entire process since poor people request help to build his house or improve current house, financial analysis, tasks scheduling of the Project, Budget creation (based on previous information about construction inputs like ground, cement, iron and so on). When a construction project is started, you can register employee’s payment and also construction inputs purchases in order to decrease project budget. Finally, it has various reports about house building goals per year or per month, per product, and metrics. Developed on CDI using JSF 2.0 with PrimeFaces 4 and PostgreSQL 9.3 database through Hibernate JPA, running on JBoss EAP 6.0, on a CentOS 6.0 x64 server .

ERP Application for medical clinic

Feb 2012 - Mar 2013 (1 year)

ERP application planning, analysis, data design and development. This ERP was customized for a medical clinic focused on ear diseases. It contains accounting module, inventory, invoices, appointments scheduling, clients tracing and a customized workshop module because they fix and create their own ear prostheses. Developed using Spring MVC with JSP, PostgreSQL 9.1 database through Hibernate JPA running on Centos 5.0 .


CS Engineer

2005 - 2011 (6 years)

Project Management Master

2014 - 2014 (1 month)


Sun Certified JAVA Programmer (2011)

Sun Microsystems

Sun Certified JAVA Programmer is a certification that assures that developer has strong knowledge about JAVA foundations.

PostgreSQL Associate Certification (2014)


The PostgreSQL Associate Certification assesses and certifies a database professional to demonstrate the fundamental skills necessary to maintain and manage a PostgreSQL server and applications in a production environment.

Oracle Certified JAVA 8 Associate (2017)


Validates knowledge of developers about the most deep features about JAVA 8 programming language


  • US English Level 1
  • HTML Level 1
  • Java Level 1


  • Facebook Disambung
  • Freelancer Keutamaan
  • Bayaran Disahkan
  • Telefon Disahkan
  • Identiti Disahkan
  • E-mel Disahkan

Kemahiran Teratas Saya

Cari Freelancer yang serupa