Senior Software Engineer, Data

Circonomit; Köln; Hybrid; EUR 90,000 - 130,000; Full time

Benefits offered by this job

Impact.

Ownership.

AI-Tooling Budget

Deutschland-Ticket

Hardware deiner Wahl

Sports membership

Job summary

Circonomit GmbH sucht eine erfahrene Backend-/Daten-Infrastruktur-Entwicklerin oder -Entwickler, die die Datenplattform für mehrere Kunden und Domänen skalieren. Sie arbeiten mit Python, TypeScript, Solid.js und PostgreSQL in einer datenlastigen Webanwendung und arbeiten eng mit dem CTO zusammen, um die Architektur zu gestalten.

Der ideale Kandidat kann End-to-End-Verantwortung übernehmen, besitzt starke Erfahrung in Datenpipelines, API-Design und CI/CD und kommuniziert proaktiv in Deutsch und

Qualifications

• Deutschkenntnisse mindestens C1; Englisch fließend.
• NRW-Standort Köln, Hybrid-Arbeitsmodell.
• Erfahrungen im Team und agilen Praktiken.

Responsibilities

• Aufbau der End-to-End-Datenplattform inkl. Ingestion, Speicherung und Abfragestruktur.
• Plattform-Schicht zusammen mit CTO: Infrastruktur, Deployments, Productionpfad.
• Leistung und Korrektheit im Optimierungs-Engine-Bereich.
• Eigene Features von Anfang bis Produktion betreuen.

Skills

5+ Jahre Backend-Entwicklung

Python

TypeScript

SQL/Analytik

PostgreSQL

Datenpipelines

API-Design

CI/CD

Teamarbeit

Deutsch C1

Englisch fließend

Tools

Solid.js

Python

TypeScript

PostgreSQL

Job description

We are building the world's decision infrastructure: the strategic twin of every industrial organization for complex combinatorial problems. We unlocked what wasn't possible before: mapping reality with its levers and constraints into a computer, then running n-dimensional optimization on critical value-chain decisions. We help Europe stay strong and the German Mittelstand make good decisions between market shifts, orders, machines and people.

Founded by Dana (CEO) and Erik (CTO) from RWTH research, backed by a €2.8M round led by Vorwerk Ventures, with customers live on our optimization models.

We move fast. We care. No patience for problems left unsolved.

Hi, I'm Erik, CTO of Circonomit. This ad is specific on purpose: you should be able to tell from it whether this is your job.

We build decision infrastructure for industrial companies: our customers model their production, with its capacities, costs and constraints, and we compute the answer to "what should we do?" before the decision is made.

Your mission: scale our data platform for multiple customers and domains. Customer data arrives in many formats from many sources, ERP exports included; it has to land in our system consistently, stay manageable at millions of records, and be fast to query when models and results are on-screen. The product is a data-heavy web app with a math-heavy backend (Python, TypeScript, Solid.js, Postgres, on Cloudflare): your center of gravity is data and infrastructure, but you touch the whole stack. We are looking for a system thinker who wants to shape the architecture.

We will not sugarcoat it: short deadlines, real workload, and a platform that grows while customers already run on it.

What you'll own

• The data platform end to end: ingestion, storage, and the query paths that keep millions of records fast on screen. You design it, you build it, you run it in production.
• The platform layer, directly with the CTO: infrastructure, deployments, and the path to production for the whole team.
• Performance and correctness work in the optimization engine, together with our research engineers.
• Your features from first line to production: nobody hands you a ticket and waits.

How we work

Small team, short lines of communication, no layers. You own your features end to end: you build them, you ship them to production yourself, you run them.

Feedback runs both ways, and it runs continuously, in daily work and in weekly one-on-ones. We talk as equals. We communicate proactively and flag it early when something isn't working out. Saying no is part of the job.

We like this work, and you'll notice. We review each other's code, and we like being together in the Cologne office, because the fastest conversations still happen in a room.

Aufgaben

Your mission: scale our data platform for multiple customers and domains. Customer data arrives in many formats from many sources, ERP exports included; it has to land in our system consistently, stay manageable at millions of records, and be fast to query when models and results are on-screen. The product is a data-heavy web app with a math-heavy backend (Python, TypeScript, Solid.js, Postgres, on Cloudflare): your center of gravity is data and infrastructure, but you touch the whole stack. We are looking for a system thinker who wants to shape the architecture.

We will not sugarcoat it: short deadlines, real workload, and a platform that grows while customers already run on it.

What you'll own

• The data platform end to end: ingestion, storage, and the query paths that keep millions of records fast on screen. You design it, you build it, you run it in production.
• The platform layer, directly with the CTO: infrastructure, deployments, and the path to production for the whole team.
• Performance and correctness work in the optimization engine, together with our research engineers.
• Your features from first line to production: nobody hands you a ticket and waits.

How we work

Small team, short lines of communication, no layers. You own your features end to end: you build them, you ship them to production yourself, you run them.

Feedback runs both ways, and it runs continuously, in daily work and in weekly one-on-ones. We talk as equals. We communicate proactively and flag it early when something isn't working out. Saying no is part of the job.

We like this work, and you'll notice. We review each other's code, and we like being together in the Cologne office, because the fastest conversations still happen in a room.

Profil

• 5+ years building production backend or data-intensive systems.
• Strong Python and solid TypeScript, with the appetite to work in both daily.
• Analytics-data experience: real SQL depth, plus any of Parquet/Arrow/DuckDB/dbt/warehouse internals.
• Production PostgreSQL (multi-tenant, migrations, performance).
• Data pipelines over heterogeneous sources (ERP exports, Excel, CSV) onto object storage (S3 or comparable), built to keep working as customers and formats grow.
• Distributed systems and API design: typical failure modes, HTTP/auth/caching, sane versioning and error behavior.
• Engineering craft: design patterns, CI/CD pipelines you set up yourself, prototypes you can throw away.
• You have worked in a team, not mostly alone, and you know from experience which agile practices carry their weight.
• You have experience working with Linear, Jira, or a similar project management tool.
• You communicate proactively, too much rather than too little, and you organize yourself and your work.
• German at C1 or better, and fluent English. Team life runs in German; code and docs are English.
• NRW-based (Cologne office), optionally Munich, Stuttgart, Berlin area or else willing to work hybrid. Open to find a way if we fit.

Nice to have:

• a substantial migration you carried out end to end (system, stack, or data)
• telemetry and observability
• Cloudflare or comparable serverless infrastructure
• frontend experience, ideally with Solid.js or another reactive framework
• optimization/OR exposure
• manufacturing or ERP data experience

You are structured and biased for action, and you have shown you play to win wherever life has put you so far.

This role is not for you if you want a clearly defined box, or work handed to you in tickets.

Wir bieten

We are a small team, pre-Series A: structures and processes are still being built, by us and by you. Priorities shift with customers, and some weeks a deadline bends the plan.

• Impact. You see your results in the real world, fast. The problems are concrete (production plans, capacities, logistics), and customers can measure in euros what your work changed.
• Ownership. What you build, you ship, and you own it once it runs. No layers between you and production, no approval chain that turns your decision into someone else's.
• The people next to you. You work directly with the CTO on the platform layer, and with the math and OR team on the optimization engine.
• Shaping. The processes are still forming, and whoever shows up with a better way of doing things gets to install it. This is a place for system thinkers: the interesting part is seeing how the pieces fit and where they will break. The company is early, and your scope will grow with it.
• Feedback speed. You will know where you stand. We say things out loud, we adjust, and we expect the same from you.
• High stakes. Competitive salary and relevant room in the equity package (VSOP) to match your contribution and your career development.
• Hardware of your choice
• AI tooling budget
• sports membership
• Deutschland-Ticket

Process: first conversation, 20 minutes, with me or with the engineer who owns our frontend. Second conversation with the two of us together; this is where the technical questions get deep. Then a hands-on challenge, about three hours of your time, followed by a 45-minute walkthrough where you explain your solution and the decisions behind it. Finally, the team: online first, then in person at the office. Both sides decide. Two to three weeks end to end, and you hear back within days after each step. Before you decide, ask us to put you on a call with someone who will tell you the good, the bad and the ugly.

Important note

Please be advised that a valid work permit for Germany is required for non-EU citizens. Unfortunately, applications without a valid work permit and sufficient German language skills may not be considered.