Billing & payment systems
Metering, invoicing, tariffs, reconciliation, payouts. The unglamorous money-movement logic that has to be correct to the cent.
Software engineering · made in Germany
We engineer software that ships.
Fintech is where we cut our teeth — but it is only one example. We build billing systems, databases, blockchain infrastructure and more. Bring us your domain; we look for how, not why not.
Full-cycle delivery · human engineers who drive AI · Deutsch · English · Русский · UG (haftungsbeschränkt), Düsseldorf
What we build
Deep where it counts, open to the rest
We have shipped real systems in these domains. We are not a fintech-only shop — fintech is just the area where our scars are deepest. New domain? That is a feature, not a blocker.
Databases & data platforms
Schema design, migrations at scale, PostgreSQL tuning, pipelines, search. Systems that stay fast as the data grows.
Blockchain & crypto
Custody, on-chain accounting, gateway integrations, MPC wallets. Our own processing runs across 9 networks and 13 gateways.
Fintech & compliance
PI / CASP-ready architectures, KYC / AML / KYT, card programs, SEPA. We have shipped this stack, not just read about it.
AI products
Domain-tuned RAG pipelines on Claude and GPT, agent workflows, evaluation harnesses. Useful wherever structured knowledge matters.
Your domain
Logistics, healthtech, internal tooling, something we have never seen — we ramp fast and ask the right questions early.
How we work
Human engineers who drive AI — across the whole cycle
AI does not replace our engineers; our engineers know how to command it. We pair senior judgement with agent-driven development to move faster without losing the plot.
Human + AI, in production
We run Claude Code, Codex and our own agent orchestrator on real repositories: agents spawn in isolated worktrees, write code and tests, run reviews and move tasks on the board. Engineers stay in charge of architecture and the hard calls. This is how we ship more, faster — not a demo, our daily workflow.
- Agent orchestration on live GitLab repos
- Senior engineers own architecture and review
- AI handles breadth; humans hold the line on correctness
The full cycle, not just the code
Shipping is the easy part. Doing it so the next team — or an auditor — can pick it up is the job.
- ArchitectureWe design before we build: data model, boundaries, trade-offs written down.
- DocumentationSpecs, ADRs and runbooks that stay useful after we leave.
- TestingUnit, integration and E2E coverage — hundreds of tests per system.
- CI/CDGitLab pipelines: lint, test, build, deploy. Green or it does not ship.
- Security & complianceSecrets management, SSO, audit logging, sanctions / KYT where needed.
- ObservabilityLogs, metrics and alerts so problems surface before users find them.
Our work
Systems we build and run ourselves
Our own roadmap is the proof of work. These are products Zentrolink owns, operates and evolves.
Crypto-fintech platform
Zentrolink Processing
Custodial wallets across 9 networks and 13 gateways, fiat ramps, card issuing, merchant acceptance and global payouts. The platform we offer fintechs as a SaaS — and the core of our own retail product.
Platform overviewSanctions screening
Compliencer
Continuous screening of counterparties against FATF and EU sanctions lists. Direct-source ingestion, KYT signals, multilingual UI. Live with paying customers.
Read the caseLegal-AI workbench
Lexflow
AI research workspace for German UWG and trademark law: a Claude RAG pipeline, saved investigations, attorney handover. In closed beta with practising lawyers.
Read the caseTreasury and incentives
Company tokens
Our own utility token, issued under MiCA once our CASP licence is in place. Designed for staking, fee discounts and partner incentives.
Coming with CASPEngagement models
Transparent pricing
We declare prices because we want the first conversation to be about your product, not our rate card. VAT is not included.
Discovery
€1,900
one-time · 1–2 weeks
A short engagement that ends in a spec, an architecture, a budget and a recommendation.
- 2–3 working sessions
- Written specification and scope
- Architecture and system diagrams
- Effort estimate and stack recommendation
MVP sprint
Most chosen from €24,000
fixed price · 8–12 weeks
A production-ready MVP with CI/CD, infrastructure and baseline compliance — built in a small, senior team.
- Backend, frontend and DevOps in scope
- One UI/UX iteration cycle
- Deployment automation and docs
- Hand-off or continued partnership
Dedicated team
from €14,000 / month
recurring, 3 months minimum · ongoing
A team of 2–4 engineers with a tech lead, operating as part of your organisation.
- Tech lead and senior engineers
- Two-week sprints, daily stand-ups
- Access to Plane.so, GitLab, Slack
- Scale up or down with two weeks notice
Hourly rate for ad-hoc work: €120 / hour. VAT not included. We sign a German-law NDA before any specifics are shared.
Why Zentrolink
Built for software that has to survive an audit
We are a German UG in Düsseldorf with senior engineers across the EU. We choose boring infrastructure on purpose — Hetzner, Cloudflare, PostgreSQL, GitLab — and we ship to production. We understand requirements fast and look for how, not why not.
No appointment needed
Send a message, get a real answer the same day — no forms, no waiting room.
Deutsch · English · Русский
We work and write in three languages, so nothing gets lost between you and the code.
How, not why not
Constraints are a design input, not an excuse. We find the path to shipped.
4
Production systems we build and run ourselves
2,400+
Commits per quarter across our products
900+
Automated tests on a single system
3
Working languages — Deutsch, English, Русский
Let's talk
Let's talk about what you want to build
Send us a short note about the product, the regulatory context and the deadline. We answer within one business day — no appointment required.
Email us [email protected]
Telegram @zentrolink
Zentrolink UG (haftungsbeschränkt) · Düsseldorf, Germany