Solutions · for enterprises

Bespoke software. Operated sovereignly. In German data centers.

We develop and operate bespoke SaaS solutions for organizations with high demands on data protection, compliance and independence — GDPR-native, free of US jurisdiction, without lock-in. From requirements through architecture to hardened operation: everything from a single source.

What we do

Development and operation — both from a single source.

Standard cloud doesn't fit every requirement. We build the solution that suits your processes and your compliance — and operate it where your data belongs.

01

Sovereign hosting

Operation in German data centers (Open Telekom Cloud) — data residency in Germany, aligned with BSI C5. On request on-premises in your own facility or fully air-gapped.

02

Bespoke SaaS

Bespoke domain applications instead of an off-the-shelf toolkit: Rust / React, local AI, multi-tenant and auditable. Test-driven, with architecture decisions documented.

03

Integration, not an island

Your software talks to your systems: SAP S/4HANA via the official APIs, OIDC / SSO, existing databases. No data silos, no shadow IT.

In SAP environments

Sovereign solutions around SAP — without mandatory SAP BTP.

We build upstream and complementary solutions that keep data sovereignty with the customer and post into S/4HANA via the official SAP APIs — on-premises or in a German data center, without any obligation to use the SAP Business Technology Platform.

Architecture: e-invoice via Fortress Invoice into SAP S/4HANA Incoming e-invoices are verified in Fortress Invoice — at your premises or in a German data center — and posted into S/4HANA via the official SAP OData API, without the SAP Business Technology Platform. At your premises or in a German data center · On-prem / air-gap E-invoice XRechnung · ZUGFeRD UBL / CII Fortress Invoice EN 16931 checking · VIES · IBAN Local AI: account assignment · touchless posting Three-way match · fraud detection SAP S/4HANA Posting of the supplier document OData API BTP optional
Fortress Invoice sits as a sovereign checking & workflow layer ahead of SAP — and posts the finished document into S/4HANA via the official OData API. Not an ERP replacement, no cloud obligation.
Request a live demo

Fortress Invoice

Sovereign accounts-payable invoice verification as an alternative to the checking & workflow layer ahead of SAP (SAP Central Invoice Management). Not an ERP replacement — posting happens in S/4HANA.

  • EN 16931 checking for XRechnung, ZUGFeRD and UBL/CII — proven rule by rule against the official standard corpus, including more than 600 official negative test cases
  • Posting into S/4HANA proven: real documents posted into an S/4HANA 2025 — purchase-order-based and against G/L accounts, via the official OData APIs, with or without SAP BTP
  • Local AI for account assignment, duplicate detection and touchless posting — fully on-premises, explainable, audited
  • Three-way match against the purchase order directly from S/4HANA · VIES VAT validation · IBAN and master data reconciliation · fraud/anomaly detection · sanctions-list screening (EU, OFAC, UK, CH, UN)
  • Tamper-evident audit log with hash chain, GoBD export — and load-tested: a full pilot year of 30,000 documents processed in 32 seconds
  • Hardened following a tool-based security assessment (RustSec, SAST, OWASP ZAP)
To the product page: Fortress Invoice
Onboarding

Four phases to go-live.

From signature to go-live: four phases, each with acceptance criteria.

PHASE 01

Installation & hardening

Operation where your data belongs: on-premises, air-gapped or in a German data center. TLS, backups with rehearsed restore, alerting.

PHASE 02

Integration workshop

Connection to S/4HANA via the official OData APIs, or handover to your middleware — including attachments and the validation report. Master-data sync, inbound channels, approval workflow mapped to your roles.

PHASE 03

Test operation & acceptance

Your real documents in a test run, acceptance against defined criteria — production starts only once everything demonstrably works.

PHASE 04

Go-live & operation

Production cut-over with a defined update and rollback path. Operated by us or by your team — continuity via verified software escrow.

How we work

Built reliably, handed over cleanly.

STEP 01

Analysis & architecture

We understand the process, cut the interfaces cleanly and record every non-trivial decision in Architecture Decision Records.

STEP 02

Test-driven development

Every rule is proven against the standard, not merely claimed. Automated tests, linting and documentation are part of the deliverable.

STEP 03

Operation without lock-in

Hardened, tenant-separated operation in German data centers — or at your premises. Source-code escrow available: you stay in control.

FAQ

What clients often ask.

What is a sovereign SaaS solution?

Software tailored to your processes and operated in German data centers — or on-premises: GDPR-native, free of US jurisdiction and without lock-in. You retain sovereignty over code and data, even after switching providers.

Can a custom solution be connected to SAP S/4HANA — without SAP BTP?

Yes. We post into S/4HANA via the official SAP OData APIs, with or without SAP Business Technology Platform. Example: Fortress Invoice verifies incoming invoices sovereignly (EN 16931, local AI, three-way match) and posts the finished document into S/4HANA via the official API — not an ERP replacement, no cloud obligation.

Where is the data hosted?

In German data centers (Open Telekom Cloud), aligned with BSI C5, data residency in Germany. On request on-premises in your own facility or fully air-gapped — entirely without an internet connection.

Which technology stack do you work with?

Rust and React, local AI (Ollama / llama.cpp), PostgreSQL. Test-driven, architecture decisions documented, multi-tenant and auditable. With source-code escrow on request.

Contact

Let's talk about your project.

Whether it's a live demo and onboarding of Fortress Invoice or an architecture workshop for your own solution — drop us a line. We get back to you personally, without funnels and without newsletter spam.

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Prefer direct? service@bruchmann-tec.com