For IT managers
Technology and way of working
How my applications are built: a shared core, versioned business modules, an interface of its own for each client and operation in containers on servers in Germany.
This page is for everyone who wants to know in more detail how I build software: IT managers, owners with a technical interest, agencies and accounting firms that work with me. In short: I do not build every application from scratch. What every business application needs comes from a shared, tested foundation. What gets developed is what makes your process special.
Four principles
A single source of truth. Every piece of information has exactly one place where it is maintained. Interfaces, reports, integrations and automations read from there instead of keeping copies of their own.
Traceable. Important steps are recorded. What is closed stays closed: in accounting, for example, posted entries can no longer be changed, only corrected by a reversing entry. The database itself enforces this, not just the interface.
Clean data before automation. Entries are checked when they are made; imports show a preview of every row before they are applied and can be undone. Automations and AI come in only once the foundation is right. Why, is explained in the post Ready for automation?
Maintainable. Business rules sit in one central place and are tested. Background jobs have a status, retry on errors and leave a log. If something fails, it gets noticed.
Four layers
| Layer | What it contains | What it means for you |
|---|---|---|
| Core | Users, login and invitations, roles and permissions, navigation, branding, background jobs, AI connection, security and operations basics | Foundations that already run in many applications instead of new development |
| Business modules | The business logic of one area, such as accounting, documents or imports, each as a package of its own with tests and database migrations | A rule is defined once and applies the same everywhere; improvements arrive in a controlled way as a new version |
| Your application | Interface, branding, roles and the logic only your business needs | The application works the way your business works |
| Operation | One container image per version, an instance of its own with its own database, servers in Germany, backups and monitoring | What gets delivered is exactly what was tested |
So the business logic lives in the module and the interface in your application. Two clients can use the same accounting logic and still have entirely different screens, roles and processes.
Building blocks in use today
This list contains only what is finished. For client projects I combine the building blocks and add what is missing.
In daily use in my own business
- Foundation: login by e-mail, invitations, roles and permissions, branding and letterhead for generated PDFs, limited login attempts, checked file uploads
- Background jobs: status, retries on errors, progress and a log for imports, reports and sending
- Accounting: double-entry bookkeeping to the German SKR04 chart of accounts, locking of periods, reversal instead of deletion, trial balance, profit and loss and balance sheet, DATEV export
- Documents: templates with placeholders, PDF generation, sending with proof
- Imports: CSV and Excel with detection of encoding and delimiter, column mapping, a preview of every row, undo
- Sending: e-mail with a queue, retries and a block list
- AI connection: one interface for text, images and speech, profiles instead of hard-wired models, fallback between providers, budget limits and a person who approves
- Website: multilingual, search engine optimisation with structured data, statistics without cookies, the initial assessment – this website runs on it
Finished and on show in the demo application
- Connections to other systems: credentials stored encrypted, connection test, status per connection
- Webhooks: receive events with a verified signature and process them, send signed events to your systems, with retries
- Staff view: a simplified interface for the phone, with the same login and the same permissions, installable as an app on the home screen
What I do not publish here
Details of servers, internal services and the security configuration are deliberately not on a public page. If you want to review the architecture, data storage or operation in a project, you get the documents for it, as well as the data processing agreement.
Frequent questions
Which technology do you work with?
Python and Django, relational databases, operation in containers on servers in Germany. The interface runs in the browser on computers, tablets and phones.
Is my application separate from those of other clients?
Yes. Every application runs as an instance of its own with its own database. If you like, it gets a server of its own.
What happens when a building block gets a new version?
Nothing at first. Your application includes every building block at a fixed version. I adopt a new version deliberately, test it and then roll it out.
Am I tied to you afterwards?
Whatever is developed specifically for you is documented. Your rights of use and a possible handover of the source code are set out transparently in the quote.