Olaf Kloecker, Full-stack Developer in Edinburgh, United Kingdom
Olaf Kloecker

Full-stack Developer in Edinburgh, United Kingdom

Member since April 1, 2016
Olaf is a full-stack Java developer and has come a long way since writing his first programs with Turbo Pascal on a handed-down home-built CP/M 80 system. He is a certified GIAC Secure Software Programmer-Java and likes to write robust and secure software which is running commercially in motorway toll collection systems, navigation devices, and security management platforms. A special interest of his is language processing.
Olaf is now available for hire




Edinburgh, United Kingdom



Preferred Environment

Bash, Vim Text Editor, IntelliJ IDEA, Windows, Linux

The most amazing...

...thing that I have researched and coded is a grapheme to phoneme converter using an artificial neural net.


  • Freelance Senior Full-stack Developer

    2017 - PRESENT
    WeatherWorks, LLC (via Toptal)
    • Consulted on hardware and software infrastructure and technologies.
    • Transformed a given design into a fully functional single page REST-backed web application.
    • Implemented all parts of the front end using React and related libraries, including different roles, user, admin, and external developer dashboards.
    • Wrote green papers on the infrastructure; opened the API for external developers, performance, and security improvements.
    • Set up AWS Linux servers and deployed the back end, front end, and dependencies (including Nginx and firewalls).
    • Engaged in problem analysis on the front end, back end, a MongoDB database, and the servers.
    • Extended a Node.js back end, improved the codebase, and fixed memory leaks.
    Technologies: Bootstrap, CSS3, Back-end, Git, Linux, Web Development, Redux, REST APIs, Full-stack, CSS, HTML5, Loopback, Node.js, Socket.IO, JavaScript, Redux-saga, React
  • Front-end Developer for Medical Streaming and Analysis App

    2020 - 2021
    Gepalon Networks Ltd (via Toptal)
    • Extended the Jitsi Meet platform to integrate artificial intelligence (neural network) generated image inference to highlight body tissue parts in a live video stream.
    • Configured and integrated Prosody modules of Jitsi Meet platform to allow token-based video conference sessions and record join end times.
    • Created Node.js and Express-based back end to store session and user information in PostgreSQL database.
    • Created user and admin dashboards to handle user meta information in relation to Jitsi Meet sessions.
    • Created Node.js back end to run TensorFlow inference as a REST service.
    Technologies: React, Node.js, MongoDB, PostgreSQL, Jitsi Meet
  • Senior Front-end Engineer

    2020 - 2020
    Brightpunch, Ltd. (via Toptal)
    • Extended the Jitsi Meet video conferencing platform to allow participants to cooperatively draw with their mouse over the moderator's video stream after being granted permission.
    • Added a custom toolbar containing shape, color, line width choosers, and undo, redo, and clear session control buttons.
    • Leveraged an internal message passing facility using a custom message format.
    • Created a CSS/JavaScript-line width chooser to use alongside the color chooser.
    Technologies: Jitsi-meet, CSS3, CSS, HTML5, Back-end, Git, Linux, Node.js, Web Development, Redux, REST APIs, Full-stack, HTML5 Canvas, JavaScript, React
  • Web Developer

    2017 - 2017
    • Created a responsive web page for mobile devices on the basis of a desktop site.
    Technologies: CSS, HTML5, Back-end, Git, Linux, React, Web Development, Redux, Full-stack, JavaScript, CSS3, Jinja
  • Freelance Senior Java Developer | Freelance Consultant

    2016 - 2017
    TradeReplay (via Toptal)
    • Consulted with clients on which technologies to use, cloud platforms, and payment providers.
    • Created the hardware and software architecture, data model, and overview diagrams for the web-based self-service members' area of a standalone desktop app to provide functionalities for registration, profile change, subscription change as well as the administrative area.
    • Developed the members' area based on Play Java with Twirl templates and Ebean ORM to PostgreSQL database.
    • Installed a system and documented the setup on a Linux server—integrating WordPress for a third-party-provided public promotional website.
    • Communicated with clients regularly, mainly through Asana, but also through email and phone—providing weekly progress reports.
    Technologies: Back-end, Play, Git, Web Development, REST APIs, Full-stack, NGINX, Linux, PostgreSQL, Bootstrap, Java, Play Framework
  • Freelance Architect | Freelance Developer

    2016 - 2017
    Freelance Work
    • Architected and single-handedly developed Trunksta.de, a social-sharing platform for sending items in other people's cars.
    • Developed the front end as a single-page application with React/Redux.
    • Implemented the back end with the Lightbend Play Java framework with an Nginx reverse proxy/load balancer and PostgreSQL database mapped to Java entities through Ebean-ORM.
    • Specified infrastructure requirements and installed the system on Linux servers.
    Technologies: Back-end, Git, Java, Play Framework, PostgreSQL, React
  • Service Consultant

    2015 - 2015
    Cellent AG (Fellbach, Germany)
    • Provided second- and third-level support for a complex legacy web-based project-management system in the automotive industry spanning a variety of frameworks and technologies.
    • Acted as the main customer contact for a major component.
    • Coordinated incident support, maintained systems, performed analysis, and fixed bugs.
    • Analyzed error reports and fixed bugs.
    • Managed the database data and structures through manual SQL commands.
    Technologies: Back-end, Confluence, Jira, Apache Struts, Jakarta EE, Java
  • Software Development Engineer

    2013 - 2014
    Dell Inc./Dell SecureWorks (Edinburgh, UK)
    • Extended and maintained complex, robust, and secure business-critical software systems for managed security services and counter-threat units.
    • Fixed bugs in a legacy Perl application for manual and automatic device maintenance.
    • Documented all parts of the newly built systems.
    • Took part in daily scrum sessions.
    • Performed user acceptance testing for newly developed features.
    • Certified as a GIAC Secure Software Programmer-Java (GSSP-Java).
    • Certified as a Cloudera Certified Developer for Apache Hadoop (CCDH).
    Technologies: Back-end, Scrum, Full-stack, OpenGrok, iBATIS, MyBatis, Confluence, Jira, FindBugs, Apache Tomcat, Ext JS, Maven, Perl, Bash, Linux, Java
  • Software Engineer

    2006 - 2013
    TomTom Software Ltd (Edinburgh, UK)
    • Supported the maintenance and improvement of the in-house continuous integration system for automated tests.
    • Created a tool to visualize a large number of trip logs into global and regional traffic heat maps.
    • Supported a navigation device platform development through testing of WebKit, automatic route testing, and embedded testing/debugging.
    • Created sample Android apps for current navigation devices to be included in an API toolkit for third parties extending the platform (e.g., Renault R-Link).
    • Developed an SVN/Maven repository crawler to check for project health, inconsistencies, missing information, prevent bit rot, ensure buildability, detect dependency cycles, and identify logical build sequences.
    • Created a RESTful web back end for a prototype device to store/retrieve data; implemented automatic tests.
    • Ported a WebDAV server from C++ to Java.
    Technologies: Back-end, JavaScript, Ajax, Apache HTTP Server, HTML, Jenkins, Maven, Android, Bash, Linux, Java
  • Professional Systems Engineer

    2001 - 2005
    T-Systems GEI GmbH (Bonn, Germany)
    • Developed a GIS application to convert a detailed digital street map into an abstract motorway graph, processing highly-complex temporally-changing data structures with graph algorithms.
    • Created a GUI program for GIS visualization of road maps.
    • Built a back end of a web booking system for toll tickets including PDF creation.
    • Supported new and junior team members to get acquainted with software.
    • Introduced static metrics (metrics, code coverage, dependency analyses) into the build lifecycle.
    • Wrote the end-user documentation for the GUI application.
    Technologies: Back-end, AWT, Swing, PDF, XML, HTML, UML, CSV, Ant, JUnit, JDBC, SQL, Java
  • Unix/Linux Systems Administrator

    1998 - 2001
    Tops.net GmbH & Co. KG (Bonn, Germany)
    • Supported and extended a Linux-based internet dial-up server for SoHo companies.
    • Created the back end of a document management system converting SGML documents into PDF files via LaTeX.
    • Managed client servers and networks.
    • Set up and installed Linux-based servers.
    Technologies: LaTeX, Perl, Bash, Unix, Linux


  • Memo Molecule

    I developed a responsive web app to create email reminders with powerful recurrence rules like "every last working day of the month" or "every third Saturday," taking into account local time zones.

    It was built with React on the front end and Node.js (Loopback/Express.js) on the back end with a MongoDB database. It also uses Semantic UI for styling and has multi-language support built in.

  • WeatherWorks Advantage

    I built a forecast management system for winter and non-winter events comprising a complex React user and admin dashboards, report pickup pages and a Node.js back end backed by a MongoDB database.

  • TRUNKSTA.DE | Social Sharing Platform

    Sole (software and infrastructure) architect and full-stack developer of a social sharing platform (no design) for the German market. Built with React.js and Redux on the front end and Java Play/PostgreSQL/Nginx on the back end. It includes all aspects of a platform including user authentication, management, admin functions, transaction email, PayPal integration, and business logic. I heavily relied on Play's reactive features, and Java 8 structures (collection streams, Optionals, and Lambdas).

    Launched in December 2016.

  • Gaelphon

    I developed a data-driven, artificial neural network-based grapheme-to-phoneme converter for Scottish Gaelic (not yet available online).

  • Time Management Systems

    I built a simple time management systems with complications in the way of multiple roles; with XSS/CSRF protection, a custom authentication API, and built with AngularJS and the Play framework.

  • Faclair Dictionaries and Grammar

    These are Scottish Gaelic/English/German dictionaries and a concise grammar text for the Scottish Gaelic language, available as Kindle e-books.


  • Languages

    JavaScript, Java, HTML, HTML5, Bash Script, XML, UML, CSS, CSS3, Bash, SQL, Perl
  • Frameworks

    Redux, Loopback, React Native, Play, TestNG, JUnit, Express.js, Apache Struts, Play Framework, Bootstrap, Jinja, Ext JS, Swing, Hadoop, iBATIS
  • Libraries/APIs

    REST APIs, Redux-saga, React, Node.js, JSON API, React Redux, Ebean ORM, AWT, HTML5 Canvas, Socket.IO, Java Security, SLF4J, MyBatis, JDBC
  • Tools

    Redux Thunk, Confluence, Jira, LaTeX, Git, IntelliJ IDEA, Subversion (SVN), Eclipse IDE, Vim Text Editor, Apache HTTP Server, Apache Tomcat, NGINX, Jenkins, Sonar, Mercurial, Perforce, Apache Ant, Maven
  • Paradigms

    REST, Agile Software Development, Object-oriented Design (OOD), Scrum
  • Storage

    JSON, MySQL, PostgreSQL, MongoDB
  • Other

    Debugging, Bug Analysis & Reporting, Web Development, Full-stack, Front-end, Front-end Development, Back-end, Code Review, Semantic UI, Ant, CSV, PDF, OpenGrok, Jitsi-meet, Ajax, FindBugs, GUI Development, TCP/IP, Jitsi Meet
  • Platforms

    Kindle, Linux, Windows, Unix, Jakarta EE, Google App Engine, Java EE, Android


  • Master of Arts Degree in Phonetics, Speech Signal Processing, Computational Linguistics, Computer Science, and Celtic Languages
    1993 - 2001
    University of Bonn - Bonn, Germany


  • GIAC Secure Software Programmer - Java, GSSP-Java
    MAY 2014 - MAY 2018

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