Linux, PostgreSQL & Bash Automation Leader

Desiderius Johannes Coertzen

United States +1-360-***-**** ****************@*****.***

South Africa +27-79-529-**** ********@*********.**.** Professional Summary

Results-driven IT professional with 15+ years of experience in software/system development, team leadership, DevOps, and large-scale infrastructure. Expert in Linux environments, PostgreSQL data warehousing, event-driven architectures, VOIP systems, and automation. Proven ability to design and maintain high-volume systems supporting millions of transactions, users, and records. Strong background in distributed systems, REST APIs, and cross-functional team leadership. Passionate about solving complex technical challenges and driving operational efficiency.

Technical Skills

Programming & Scripting: SQL (20 years), Bash (19 years), Python (6 years), PHP (7 years), JavaScript (7 years), HTML/CSS, Lazarus Free Pascal (16 years) Databases & Data Engineering: PostgreSQL (17 years, including PL/pgSQL), MySQL/MariaDB

(14 years), MS SQL Server (10 years), Redis (2 years), Oracle, SQLite; Data warehousing, ETL, performance tuning, parallelization

Operating Systems & Infrastructure: Linux (OpenSUSE, Debian, Raspbian, CentOS – 15+ years), System administration, Networking (NGINX, firewalling, routing, VPNs), Virtualization

(KVM, Proxmox, LXC)

Key Technologies: Asterisk (VOIP/PBX), REST APIs, Redis job queuing, Git/Subversion, Event- driven & distributed architectures, Bash automation, Hardware integration (telemetry, GPS, serial/GSM)

Other: Agile/DevOps practices, Source control & release management, Disaster recovery, Web development (Vanilla JS, Bootstrap, Tailwind)

Professional Experience

Software Development Manager / Team Lead / System Developer Workforce Group South Africa 2010 – 2025

Led development and operations for a major staffing platform supporting 38,000 contractors, 434,000 job applications, and 360,000 contracts.

Architected and maintained a high-volume PostgreSQL data warehouse processing over 1.2 billion records in daily intake, using Python, Bash scripting, and performance optimization techniques.

Designed and managed VOIP infrastructure handling 7.19 million calls, 172,000 hours of voice logging, and 3.2 million customer messages.

Built distributed, redundant, event-driven systems with REST APIs, Redis-based job queuing, and automation via Bash and custom tools.

Served on the IT Steering Committee and coached team members while implementing selected Agile and DevOps practices.

Oversaw system administration, database management, and support for Linux environments.

Deployment Specialist / Operations Quality Control Cartrack Europe Europe (Portugal, Poland, Spain) 2009 – 2010

Successfully deployed vehicle tracking and fleet management operations across three European countries.

Integrated three cellular location-based services and implemented two mass telemetry solutions.

Configured IPSec VPNs with cellular providers for secure cross-border operations. Software Developer / System Developer

Cartrack Onecell Technologies South Africa 2004 – 2009

Developed production testing systems and tools for vehicle tracking hardware, processing 400 units daily (PCB jig-testing, firmware loading, and database registration).

Instrumental in R&D and testing systems for four new products.

Built backend systems handling 100,000 PDU SMS telemetry messages and remote firmware upgrades for 50,000 units.

Delivered control room capabilities supporting 200,000 vehicle tracking units with mapping functionality.

System Developer (Contracted to Babereki Finance Division) Workforce Group South Africa 2004 – 2009

Developed mass SMS platform supporting 20,000 recipients.

Implemented automated cellular prepaid voucher dispensing and USSD-based airtime transfer systems for 10,000 users.

Software Developer

Cellsecure South Africa 1999 – 2002

Developed control room monitoring systems with capacity for 1,000 units.

Implemented small-scale cellular triangulation for electronic security applications. Additional Information

Extensive hands-on experience with hardware integration, serial/GSM/GPS communications, Raspberry Pi/ARM development, and custom binary tooling.

Broad exposure to networking, telephony (Asterisk), virtualization, web technologies, and open-source ecosystems.

Continuously updated technical skills (last major update: August 2025).

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