Luca Killmaier

Freelance software engineer

Work
Case study
Under NDA

Edge platform for smart-meter value-added services

Freelance software engineer (Go / embedded Linux) · 2023–2025 · Energy / Smart Metering

Go-based on-device service platform for an embedded smart-meter-gateway add-on module that securely hosts containerized third-party energy apps. Extended over 2.5 years with mutually-authenticated MQTT/TLS, signed OTA updates, and automated CVE screening.

Outcome

9→1

services consolidated into one daemon

600+

commits shipped

2.5+ yrs

engagement

The CVE-screening pipeline became a standard, release-gating CI stage for the whole platform.

Context

A German energy-technology manufacturer ships an embedded Linux device that attaches to certified smart meter gateways (CLS channel) and runs value-added energy applications in containers. The on-device platform needed hardened backend connectivity, a secure update chain, and continuous feature development.

What was done

Mutual-TLS MQTT connectivity

Designed and built mutually-authenticated MQTT-over-TLS backend connectivity end to end, with on-device X.509 PKI and certificate lifecycle APIs (Go, gRPC/REST, Paho).

Signed OTA updates

Added signature verification of firmware and application images in the OTA path and hardened the A/B update state machine and its rollback behaviour.

Resilient CLS channel

Hardened the device-to-backend channel through the smart-meter-gateway CLS tunnel with reconnect and fallback logic, a publish queue and connection monitoring.

Service consolidation

Consolidated nine separate services into a single multiplexed daemon to cut the footprint on the resource-constrained ARM target.

Automated CVE screening

Introduced automated CVE screening as a CI stage, with report generation and verdict tracking across releases.

Container app hosting

Extended container-based app hosting: configuration and secret injection, bind mounts, log rotation and restart policies via the Docker SDK.

Stack

Backend

Go
gRPC
grpc-gateway (REST)
Protobuf
MQTT (Paho)
PostgreSQL
GORM
OAuth2/JWT

Embedded / Infra

Embedded Linux (Yocto)
systemd
Docker (on-device)
QEMU
GitLab CI
A/B OTA updates

Security

X.509 PKI
mTLS
artifact signing
CVE screening
SBOM (CycloneDX)

© 2026 Luca Killmaier