Key Engineer (Staff / Principal Level) – Backend, Infrastructure & IoT

Key Engineer (Staff / Principal Level) – Backend, Infrastructure & IoT

Berlin | Full-Time | Start ASAP

We're looking for an exceptional engineer. A true A-player who wants to take ownership, build world-class technology, and play a key role in shaping the future of Heidi Systems.

About Heidi Systems

Submetering in Germany still runs mostly on paper. Meters get read by hand, data sits in PDFs, and tenants see their consumption once a year.

Heidi Systems changes that end to end. We install meters and gateways in buildings, collect the data and build the platform property managers use to monitor consumption and run the yearly utility billing.

We have paying customers, a growing pipeline and an angel round with unicorn founders and directors from Google and OpenAI. Now we need an engineer who can carry a big part of the technical foundation together with the founders.

The role

You'll be one of the technical leads at Heidi and work directly with the founders. You make the architecture decisions, build them yourself and run them in production.

As the team grows, you'll help hire and mentor the next engineers.

What you'll own

• Backend services in Go and TypeScript, including the API our SvelteKit frontend talks to

• Microservices: deciding where to split services and building them, mostly in Go

• Data pipelines: ingestion, validation and processing of meter, gateway and building data. These numbers end up on invoices, so they have to be right.

• Databases and storage: PostgreSQL, Supabase and S3. Schema design, performance, backups, replication.

• IoT and connectivity: MQTT, message brokers, wireless gateways and the bugs that only show up with real hardware in a basement

• Infrastructure and deployments: Hetzner servers, Docker, Caddy, GitHub Actions, GHCR

• Monitoring and incidents: logging, alerting and a clear process for when something breaks

• Engineering standards: code review, testing and how we ship

What you bring

• A track record of building backends that run in production, and that you owned yourself

• Experience writing production backends in Go and TypeScript

• Experience with Supabase, or with PostgreSQL and S3

• Experience designing and running microservices, ideally in Go

• Hands-on with Docker and deploying to Linux servers

• You've set up monitoring, logging and alerting before

• You debug production issues yourself and can explain afterwards what went wrong

• You've made architecture decisions on a real product and can walk us through the trade-offs

• Fluent English

Bonus points

• Real-time systems, especially MQTT and message brokers

• Building CI/CD pipelines and DevOps setups

• AI data pipelines

• High-volume time-series data

• Bare-metal or VPS infrastructure, ideally Hetzner

• Experience in energy, PropTech or infrastructure tech

• Previous role as founding engineer, tech lead, staff or principal engineer

• Hiring and building engineering teams

Our stack

• Languages: Go, TypeScript

• Data: PostgreSQL, Supabase, S3

• Infrastructure: Hetzner, Docker, Caddy

• CI/CD: GitHub Actions, GHCR

• Connectivity: MQTT, IoT data streams, APIs

• Config: YAML, TOML

We care more about how you make engineering decisions than whether you know every tool on this list.

Why Heidi

• You work directly with the founders. Most decisions take one call.

• You own core systems from day one and set many of the standards the team builds on.

• The problems are real: software, hardware and energy data in buildings across Germany.

• A renovated Altbau office in Berlin Mitte at Monbijoupark, everyone at one table.

• Room to grow into a lead role as the engineering team gets bigger.

Location

Berlin, on-site. You live in Berlin or are willing to move. Full-time, start as soon as possible.

How to apply

What you've built matters more to us than your CV. Send us:

• A short intro and your CV or LinkedIn profile

• Your GitHub profile or other examples of your technical work

• One complex system you designed, built or ran in production. Tell us what made it hard, which architecture decisions you made, what went wrong and how you fixed it.

We're looking for someone who wants to become one of the engineers behind a category-defining company.

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