David is available for hire
Hire DavidDavid Calloway
Verified Expert in Engineering
Software Developer
Location
Woltersdorf, Germany
Toptal Member Since
June 21, 2022
David is a man fascinated by both human and computer languages. In his spare time, he's equally likely to be rereading the Bash manual pages, perusing his German dictionary (Duden), or listening to podcasts when he does the inevitable menial tasks required by life. His favorite programming languages all feature functions as first-class citizens.
Portfolio
JACOB Elektronik GmbH
Go, GitLab, GitLab CI/CD, CI/CD Pipelines, Terraform, ECS...
Bornemann AG
Java 9, Docker, Bash, Node.js, RabbitMQ, Postfix, PostgreSQL, MongoDB, Mongoose...
Bornemann AG
JavaScript, Node.js, RabbitMQ, MySQL, PHP, MySQLi, DOM, jQuery, jQuery UI...
Experience
Availability
Part-time
Preferred Environment
Linux, Emacs, Email, Git, Bash
The most amazing...
...service I've provided is to keep all production services running through major stack migrations, ultimately transitioning to a microservice-based platform.
Work Experience
Software Developer
2023 - PRESENT
JACOB Elektronik GmbH
- Developed a fully-tested, high-level AMQP client library for broad use within the company, which reduced boilerplate code and increased reliability for message-backed microservices.
- Contributed to multiple open-source libraries, including fixing a race condition in the most popular AMQP library for Go.
- Shared accumulated knowledge regularly in the form of versioned documents during the process of evaluation and developing solutions.
- Provided assistance to our team in designing backward-compatible services to progress toward long-term goals without downtime.
Technologies: Go, GitLab, GitLab CI/CD, CI/CD Pipelines, Terraform, ECS, Amazon Elastic Container Service (Amazon ECS), Git
Head of Back-end Development
2016 - 2020
Bornemann AG
- Created a system to anonymize and export tracking data of approximately 20,000 vehicles daily for licensed third parties.
- Updated several public and internal APIs to support authentication via a newly-developed centralized authentication and authorization server.
- Developed module for exporting historical vehicle data with cryptographic signatures, allowing export origin verification beyond normal in-system data lifetime.
- Transferred over 15,000 legacy event notification rules into under 1000 simplified rules for new event notification systems by factoring parameter sets from their Cartesian products. This avoided having customers re-key notification parameters.
Technologies: Java 9, Docker, Bash, Node.js, RabbitMQ, Postfix, PostgreSQL, MongoDB, Mongoose, JSON, PHP, APIs
Head of Software Development
2009 - 2015
Bornemann AG
- Led development of our flagship product, Infleet Online, serving thousands of customers to track thousands of vehicles. This customer-facing product included live vehicle tracking, event handling, presentation of historical data, and more.
- Developed an internal management tool for supporting operations, including dispatching inventory to customers, remote GPS tracker communications, and generating aggregated reports for business purposes.
- Assisted in integrating various third-party tools with our products based on customer needs.
- Built a complete REST API accessible by customers, giving full programmatic access to all back-end features.
- Created custom niche solutions for specific customers based on business needs and budget.
Technologies: JavaScript, Node.js, RabbitMQ, MySQL, PHP, MySQLi, DOM, jQuery, jQuery UI, Google Maps, PostGIS, PostgreSQL, Jira, MongoDB, MariaDB, RHEL, Debian Linux, SQLite, Git, Mercurial, Subversion (SVN), Django, DataTables, Microsoft SQL Server, WebSockets, Express.js, Postfix, Java, Linux Server Administration, API Integration, Amazon Web Services (AWS), SQL, NGINX, APIs
Front-end Developer
2007 - 2008
Bornemann AG
- Converted existing front-end prototype away from using a custom mixed-language PHP and JavaScript function to Ajax and JavaScript-only calls using a library.
- Converted a multi-page map-based tracking application to a single-page application, reducing the company's licensed map usage and allowing customers to see various mapped data without switching pages.
- Assisted the back-end team in developing a REST API for the front-end work, allowing more loose coupling of these separate concerns.
Technologies: MySQL, jQuery, jQuery UI, MooTools, YUI, YUI Compressor, JavaScript, Ajax, PHP, APIs
Junior Developer
2006 - 2006
Appalachian Technologies
- Crafted weather graphs and visualizations with loving attention to minor details.
- Performed minor maintenance for small business websites.
- Provided support for dial-up internet service customers.
- Performed antivirus, software tuning, and computer repair.
Technologies: PHP, MySQL, HTML, CSS, SQL
Experience
Infleet Online
https://bornemann.net/gps-fahrzeugortung/A live and historical vehicle and sensor tracking web application oriented toward small to medium businesses. Infleet provides live tracking on a map with additional tools for dispatch planning.
For historical data, it is possible to visualize and replay tracking data and generate various reports based on the collected data. Report generation was available on-demand in the browser or periodically by configuration to send as email attachments.
Various event handling tools were available, most commonly notifications of specific events. Event handling included vehicle data collection, such as ignition status, speed, acceleration, and location data like GPS geofencing or changes of mobile network operators.
All functionality from the web interface was made available via a REST API, including registering event handlers as HTTP calls.
For historical data, it is possible to visualize and replay tracking data and generate various reports based on the collected data. Report generation was available on-demand in the browser or periodically by configuration to send as email attachments.
Various event handling tools were available, most commonly notifications of specific events. Event handling included vehicle data collection, such as ignition status, speed, acceleration, and location data like GPS geofencing or changes of mobile network operators.
All functionality from the web interface was made available via a REST API, including registering event handlers as HTTP calls.
FirmUp
An over-the-air firmware updater application that applied upgrades to GPS tracking devices remotely, enabling new features and ensuring continued operations. I was the full-stack developer and maintainer for this project.
One interesting aspect of this project was incorporating an existing database of available device types matched to possible firmware upgrades. Available upgrades were deployed in an automated rate-limited fashion to avoid the possibility of overwhelming our support team.
One interesting aspect of this project was incorporating an existing database of available device types matched to possible firmware upgrades. Available upgrades were deployed in an automated rate-limited fashion to avoid the possibility of overwhelming our support team.
ConFix
A Node.js-based application to prepare and apply device settings for GPS tracking devices. I was the full-stack developer and maintainer of this project, assisting our support staff's daily operations.
One interesting aspect of this project was its flexible design that could handle new device models via a set of parameter conversions. Using these parameter conversions allowed support staff to generate universally-applicable configurations based on the desired behavior rather than specific parameters for a particular model.
A further useful feature of the project was the live updates of running configuration tasks, which allowed support staff quick feedback.
This project was split into two services that communicated with each other (and further services) for better integration with additional service software.
One interesting aspect of this project was its flexible design that could handle new device models via a set of parameter conversions. Using these parameter conversions allowed support staff to generate universally-applicable configurations based on the desired behavior rather than specific parameters for a particular model.
A further useful feature of the project was the live updates of running configuration tasks, which allowed support staff quick feedback.
This project was split into two services that communicated with each other (and further services) for better integration with additional service software.
Education
2015 - 2021
Master's Degree in Computer Science
Hochshule Trier - Trier, Germany
2000 - 2005
Bachelor's Degree in Spanish and German
Appalachian State University - Boone, NC, USA
1996 - 1998
High School Diploma in Mathematics
NC School of Science and Mathematics - Durham, NC, USA
Certifications
NOVEMBER 2006 - PRESENT
Sun Certified MySQL 5.0 Developer
Sun Microsystems
FEBRUARY 2006 - PRESENT
Zend Certified Engineer
Zend Technologies, Inc.
Skills
Libraries/APIs
Node.js, jQuery, jQuery UI, Google Maps, AMQP, Moment.js, Socket.IO, MooTools, YUI
Tools
RabbitMQ, Emacs, Postfix, NGINX, Mongoose, Jira, Git, Mercurial, Subversion (SVN), DataTables, YUI Compressor, GitLab, GitLab CI/CD, Terraform, Amazon Elastic Container Service (Amazon ECS)
Languages
JavaScript, HTML, Bash, CSS, Java, SQL, PHP, HTML5, Go, PHP 5, Java 9, Python
Frameworks
Express.js, Django
Storage
JSON, MySQL, MongoDB, MariaDB, MySQLi, PostGIS, PostgreSQL, SQLite, Microsoft SQL Server
Platforms
Linux, Android, Embedded Linux, Debian Linux, Amazon Web Services (AWS), Docker
Paradigms
REST
Other
German, Ajax, Spanish, Email, Linux Server Administration, API Integration, APIs, Spanish-English Translation, Computer Science, Mathematical Modeling, DOM, RHEL, WebSockets, SMS Gateways, Kannel, Bluebird, CORS, CI/CD Pipelines, ECS
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