Patrik Zrinyi
Magyar

Patrik Zrinyi

Software engineer, backend and infrastructure

Portrait of Patrik Zrinyi

I build backend systems

and know the infrastructure they run on.

Software engineer at Rackhost. On the application side I work with PHP and PostgreSQL; underneath, with Docker, Xen and Proxmox. In my own time I build things end to end, from the firmware on a cellular GPS tracker to the dashboard that reads its data.

Experience
3+ years at Rackhost
Education
BSc in Computer Science, University of Szeged
Based in
Hungary

About

I am most effective where system-level thinking meets hands-on delivery. Since 2023 I have worked at Rackhost as a software engineer, mostly on backend and infrastructure-adjacent problems: integrating third-party systems into the platform, designing PostgreSQL schemas and triggers, and keeping Docker-based development environments predictable for the whole team.

Alongside the application work I have grown into the layer below it: virtualization with Xen and Proxmox VE, backups with Proxmox Backup Server, custom OS images provisioned through cloud-init, and the CI/CD pipelines that tie it all together. I care about reliability, a codebase people can read, and environments that behave the same everywhere.

  • Backend depth

    PHP/Yii applications, REST APIs and PostgreSQL done properly: schema design, triggers, PL/pgSQL and time-series data with TimescaleDB.

  • Infrastructure mindset

    I know what happens below the application: containers, virtual machines, images, backups and pipelines. What I build is meant to be deployed, backed up and restored.

  • End-to-end ownership

    My side projects run from firmware to dashboard. I like owning a problem all the way through, including the unglamorous parts.

The stack, top to bottom

Application

  • PHP (Yii2)
  • REST API design
  • JavaScript
  • Python
  • Go

Data and streaming

  • PostgreSQL
  • PL/pgSQL and triggers
  • TimescaleDB
  • Redis
  • Apache Kafka
  • MySQL
  • MongoDB

Containers and OS

  • Docker
  • Linux
  • SaltStack

Virtualization

  • Xen
  • Proxmox VE
  • Proxmox Backup Server
  • cloud-init
  • Custom image building

Across every layer

  • CI/CD pipelines
  • GitHub Actions
  • Git
  • Grafana

Experience

  1. 2023–presentHungary

    Software Engineer

    Rackhost Zrt.

    • Integrate and customize third-party systems into the Rackhost platform.
    • Design new PostgreSQL tables and write triggers for platform features.
    • Optimize Docker-based development environments and bring new modules and services into the existing architecture.
    • Work with the virtualization layer (Xen, Proxmox VE, Proxmox Backup Server) and build custom OS images provisioned with cloud-init.
    • Build and maintain CI/CD pipelines.
    • Collaborate with system operators and developers on infrastructure projects, such as introducing new services and integrating them into existing systems.
    • Front-end development: full UI redesigns and larger features, built with Bootstrap and custom CSS.

Side projects

Three side projects, one habit: get data out of real devices, store it properly, and make it useful.

Vehicle GPS tracker

Main project2024–present, in daily use

A cellular GPS and OBD-II tracker for my car, built end to end: custom firmware on an ESP32-S3 with a SIM7080G modem, a REST API, a time-series database and a live map.

  1. ESP32-S3 + SIM7080GGNSS, OBD-II, LTE-M
  2. REST APIYii2, bearer auth
  3. TimescaleDBhypertables, PL/pgSQL
  4. Live mapLeaflet, SSE
Firmware built for the real world
A state machine with adaptive sampling (every 10 s when moving, every 2 min when parked), a flash-backed queue that survives power loss, exponential backoff with jitter, deep sleep and over-the-air updates.
Trips detected inside the database
PL/pgSQL functions run as a TimescaleDB background job, inferring ignition from gaps in the telemetry and filtering out GPS drift. Hypertables and continuous aggregates keep the queries fast.
Live map and history
A Leaflet map streamed over Server-Sent Events, track playback, OBD-II charts, an operating log, CSV export and offline import from SD card.
Shipped like a product
A Docker Compose stack, GitHub Actions deployments on version tags, and around 34 automated tests.

Built with: C++ (Arduino), ESP32-S3, SIM7080G LTE-M, PHP 8 (Yii2), PostgreSQL, TimescaleDB, Leaflet, Docker, GitHub Actions

AirFlow Manager

2025, self-hosted

Self-hosted monitoring and alerting for AUX air conditioners, which otherwise only talk to a closed cloud app.

  1. AUX cloud APIAES, reverse-engineered
  2. CollectorPHP, cron
  3. TimescaleDBhypertable
  4. Dashboard and alertsYii2, e-mail
Ported a reverse-engineered client
Re-implemented the community Python client for the AUX cloud in PHP: AES-encrypted login flow, region-aware endpoints, multiple accounts and units.
Time-series collection
A cron-driven collector snapshots around 22 parameters per unit into a TimescaleDB hypertable.
Rule-based alerts
E-mail notifications for power transitions, temperature thresholds, lost connections and a cooling-efficiency check, throttled per unit and alert type.

Protocol knowledge comes from the open-source project maeek/ha-aux-cloud

Built with: PHP 8.3 (Yii2), PostgreSQL 17, TimescaleDB, Chart.js, Docker Compose

Tesla Wall Connector to Grafana

Home energy monitoring

Charging data from a Tesla Wall Connector, collected through the charger’s API and turned into Grafana dashboards.

  1. Wall Connectorcharger API
  2. Collectorpolling service
  3. TimescaleDBPostgreSQL
  4. Grafanadashboards
Collector service
Polls the Wall Connector API and stores every reading as time-series data in PostgreSQL with TimescaleDB.
Grafana on plain SQL
Dashboards query the database directly: charging sessions, power and energy over time.

Built with: PostgreSQL, TimescaleDB, Grafana

Education

  1. 2021–2025

    BSc in Computer Science

    University of Szeged

    Thesis: a web interface for Redmine migration.

Contact

Let’s talk.

Working on something where backend and infrastructure meet? I am happy to talk.