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Custom software development in Munich

Software development for companies and startups: Streng Labs builds websites, web applications, SaaS platforms, backends and mobile apps, as new software or as an extension of a system you already run.

You work directly with the software developer who plans and builds your project, in German or English. Client work follows the same standards as our own products: typed code, automated tests, documented architecture and repeatable deployments.

We take on a small number of projects at a time, so each one gets the attention it needs.

Start a project enquirySee how a project runs

Most asked for

  • Websites

    For small businesses, trades and practices: designed and built individually, with help with domain, hosting and e-mail.

  • Web applications and MVPs

    The first version of your product for real users, as a web app or mobile app, with accounts and payments if needed.

  • Modernisation

    Develop running software further: new features, Angular updates and taking over code from previous developers, step by step.

Typical situations

Most projects start from one of these situations.

  • Your processes run on spreadsheets and e-mail

    A web application replaces the spreadsheet: shared data, roles and permissions, and exports for accounting or other systems.

  • Your existing software needs to grow

    New features, a current framework version or a new interface for an application that is in daily use, without starting from scratch.

  • You need a first version for real users

    An MVP with a clearly limited scope, with accounts and payments, built so it can be developed further.

  • Your systems need to work together

    An API or integration that connects your application with partners, payment providers or accounting, with documented interfaces.

  • Your users need an app that works offline

    A mobile app that also works without a connection and stores data on the device in encrypted form.

  • You want a sound basis for a decision

    A technical concept with architecture, technology choice, effort and risks, before you commit to a build or a tender.

What we build

Seven kinds of work, each with what you receive at the end.

  1. Web applications and SaaS

    Web applications and SaaS platforms, full-stack from database to user interface, for example with Angular and .NET or Java, with accounts, roles and payments where you need them.

    What you receive

    • Frontend and backend as one system
    • Sign-in, accounts and roles
    • Payment provider integration

  2. Websites with design and hosting help

    A modern website for your business, from design to launch: fast, easy to read on every phone, findable on Google, with a contact form or appointment request where it helps. We also help with domain, hosting and e-mail. This website is built the same way.

    More on Websites

    What you receive

    • Design that fits your business
    • Fast, responsive and ready for search engines
    • Help with domain, hosting and e-mail

  3. MVP development

    A first version with a clearly limited scope that real users can work with. Built so it can grow instead of being thrown away.

    More on MVP development

    What you receive

    • Prioritised feature scope
    • Working first release
    • Plan for the next steps

  4. Extension and modernisation of existing software

    New features for software in use, and step-by-step updates while it keeps running.

    More on Modernisation

    What you receive

    • Assessment of the current code
    • Step-by-step plan
    • New features with tests

  5. APIs, backends and integrations

    Backends and APIs that your applications and partners can rely on, with clear contracts and versioning. Also e-invoicing in your own software: creating ZUGFeRD invoices or reading XRechnung files, as in ZugNow.

    What you receive

    • Documented REST API
    • Integrations with existing systems
    • Logging, monitoring and alerts

  6. App development with Flutter

    Apps for Android and iOS from one Flutter codebase, offline-capable where your users need it.

    What you receive

    • Flutter app for Android and iOS
    • Encrypted local storage
    • Store release preparation

  7. Technical concept and architecture

    A technical concept before the first line of code, so that decisions on stack, hosting and structure are made deliberately.

    What you receive

    • Architecture document
    • Technology recommendation
    • Effort and risk assessment

Technologies

Tools from our own products and from years of project work in automotive, enterprise and industry. Our web products are built with Angular: Angular development for new applications, plus further development and upgrades of existing Angular projects. Other stacks we assess before we commit.

More about the studio
Web
Angular, TypeScript, NgRx, Blazor
Backend
C# / .NET, ASP.NET Core, Java / Quarkus, REST, gRPC
Data
PostgreSQL, Azure Cosmos DB, SQL
Desktop
WPF
Mobile
Flutter, Dart
Operations
Docker, Linux, Microsoft Azure, Hetzner, Cloudflare, CI/CD

Our own products as reference

Judge our work by what we build for ourselves. These are in-house products, not client projects. ZugNow is available; the others are in development.

In-house development

ZugNow: e-invoicing for small businesses

A web app that creates invoices as PDF with embedded ZUGFeRD data, for freelancers and small businesses in Germany.

Technology
Angular, TypeScript, Java / Quarkus, Microsoft Azure, Terraform
Relevant for
Business software with legal requirements, payments and sensitive data
View product page
  • ZUGFeRD 2.x XML is generated and embedded into the PDF with the Mustangproject library.
  • Before an invoice is finalised, the backend checks the mandatory details under § 14 UStG.
  • Bank and tax details are stored with field-level AES-256-GCM encryption.
  • Payments via Stripe: each webhook event is processed only once, and a scheduled job reconciles subscriptions with Stripe.
  • The Azure infrastructure is defined as code with Terraform, including monitoring and alerts.

In-house development

ModernVitae: CV and job application manager in the browser

A web app for CVs, cover letters and job applications, with a companion extension for Chrome and Edge.

Technology
Angular, NgRx, C# / .NET, PostgreSQL, Docker, Linux
Relevant for
Web platforms with accounts, browser integration and mobile use
View product page
  • 62 CV templates; the PDF comes from the browser's print engine, so preview and download break pages the same way.
  • An existing CV in PDF form is read locally with PDF.js; the file does not leave the browser.
  • The Manifest V3 extension requests only the permissions it needs and signs in with PKCE, short-lived access tokens and rotating refresh tokens.
  • Installable as a web app; on the phone it appears in the share menu, so job ads can be saved from other apps.
  • ASP.NET Core backend in clean architecture with PostgreSQL; every architecture decision is recorded.

How a project runs

  1. Initial conversation

    A free, non-binding conversation of up to 30 minutes about your goal, timeline and budget. You find out early whether we are the right fit, before you invest time in details.

  2. Scope and concept

    We define the scope together. You receive a technical concept that describes what will be built and how. The concept is paid; if you commission the project, only a small part of it is charged.

  3. Proposal

    You receive a written proposal with scope, milestones and costs. Development starts only once you have accepted it.

  4. Development in milestones

    We build in short iterations. At every milestone you see working software and have access to the repository.

  5. Launch and handover

    We put the software into operation with you and hand over code and documentation, or agree on continued operation and maintenance.

Start a project enquiry

Portrait of Sebastian Streng
Sebastian StrengOwner and developer

What you can rely on

Direct contact
You talk directly to the person who writes your code, without account managers in between.
Visible progress
You have access to the repository and see progress at every milestone, not only at the end.
Clean handover
Code, documentation and deployment are set up so that another team can take over.
Code and rights of use
Once the project is paid for, you receive the source code and the rights of use agreed in the contract.

Is this the right fit?

This helps you judge early whether working together makes sense.

A good fit

  • Companies with a concrete software need
  • Companies that want to extend or modernise software they already run
  • Startups and founders with a budget for the project
  • Projects with a rough timeline
  • Products that are meant to be used and developed over years

Not a fit

  • Equity-only or unpaid work
  • Ideas without funding or budget yet
  • Projects that need a large team from day one

Frequently asked questions

Why are there no prices on the website?

Every project has a different scope. The initial conversation is free and non-binding and takes up to 30 minutes. A concept is paid work; if the project is then commissioned, only a small part of it is charged. Before development starts you receive a written proposal with scope, milestones and costs.

Who gets the source code?

Once the project is paid for, you receive the source code and the rights of use agreed in the contract. The contract states the details for your project.

Can you work on our existing software?

Yes. We start with an assessment of the code and how it is run, then agree on a step-by-step plan. Technologies we do not use ourselves we assess first, and we tell you openly whether we are the right choice.

What happens after launch?

You decide: we hand over code and documentation so that your team or another provider can continue, or we agree on operation, maintenance and further development.

In which languages do you work?

German and English, written and spoken. You work with a software developer based in Munich.

Which project sizes are a good fit?

Projects that one experienced developer can plan and build with a clear scope: a new application, an MVP, an extension of existing software or a technical concept. Projects that need a large team from day one are not a fit.

Custom software or a standard product?

If a standard product covers your process well, it is usually the better choice, and we say so in the initial conversation. Custom software makes sense where your process sets you apart, where standard tools force workarounds, or where systems have to be connected.

Do you also work for private individuals?

The focus is on companies and startups. Private projects with a clear scope and budget, such as a website, are not excluded; describe yours in the form.

Tell us about your project

Describe what you want to have built, your timeline and your budget range. You get a personal reply from the person who would work on your project.

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