Sven Kubiak Java and backend development

I am Sven Kubiak, a software developer in Germany focused on Java and backend development: web frameworks, REST APIs, authentication and multi-tenant systems that are straightforward to run yourself.

I have been building and running Java applications for over 20 years. Much of that work is open source on GitHub, and several libraries are on Maven Central. I also build the occasional iOS app in Swift.

View projects GitHub
  • 7Open-source projects
  • 4Libraries on Maven Central
Beta
Current project

Paprika: Self-hosted backend for multi-tenant apps

Paprika is a self-hosted backend as a service. Each tenant gets its own database, its own users and its own files. Paprika runs as a single Docker container on your own server, with no dependency on a cloud provider.

getpaprika.dev ↗ Documentation Source code on GitHub
  • A separate MongoDB database per tenant
  • REST API, authentication and access rules
  • Realtime events, webhooks and file uploads
  • Admin interface, Docker image or .deb package
iOS apps

Apps for iOS

Alongside the backend work, I build the occasional app in Swift and SwiftUI.

All on the App Store →
Abentoo app icon

Abentoo

Travel · Camper

A planning app for trips with a motorhome or camper van: routes and stops, bookings and documents, checklists and a trip logbook.

  • Trip planning
  • Logbook
  • iOS 26
App Store abentoo.de ↗
Moodama app icon

Moodama

Health · Mood tracker

A simple mood tracker: record a mood quickly and see patterns over time. No sign-in or account required.

  • Mood journal
  • No account
App Store
Microlocate app icon

Microlocate

Utilities

Records the current location and sends it to your own server, either on a schedule or by distance.

  • Location
  • Self-hosted
App Store
Filed Papers app icon

Filed Papers

Bookmark manager

A bookmark manager for a self-hosted Filed Papers server. A share extension saves links straight from Safari.

  • Open Source
  • Self-hosted
App Store Server on GitHub ↗
My Software app icon

My Software

Developer tools

Release planning for developers: projects, versions, issues and tags in one place.

  • Release planning
App Store
Open Source

Open-source projects

Frameworks, servers and libraries for Java, mostly under the Apache 2.0 license.

All repositories →
svenkubiak / mangooio

mangoo I/O

A lightweight full-stack web framework for Java, built on Undertow. Classic MVC with established libraries. Currently at version 10, and the foundation of Paprika, Karakal and Filed Papers.

Java 62 Apache 2.0 Maven Central
svenkubiak / karakal

Karakal

A self-hosted identity provider for passwordless sign-in with WebAuthn, placed in front of existing applications.

JavaDocker
 svenkubiak / filedpapers

Filed Papers

A self-hosted bookmark manager with a focus on privacy. The server for the iOS app of the same name.

JavaDocker
 svenkubiak / embedded-mongodb

embedded-mongodb

Starts an embedded MongoDB instance for unit tests and local development.

Java 16 Maven Central
svenkubiak / JPushover

JPushover

A Java client for the Pushover API, synchronous or asynchronous. 18 KB, with no external dependencies.

Java 12 Maven Central
svenkubiak / simple-http

simple-http

A thin wrapper around the JDK HTTP client for GET, POST, PUT, PATCH and DELETE.

Java 5 Maven Central
Profile

About

I build backend software in Java: web frameworks, APIs and servers you can run yourself. The focus is lean, maintainable architecture, multi-tenancy and privacy.

Backend

Java backends with mangoo I/O and Undertow: REST APIs, authentication and Maven builds. The focus is a lean architecture that stays maintainable without a large framework around it.

Data

MongoDB with a separate database per tenant, plus realtime events when data changes. Files and access rules stay with that tenant.

Operations

Runs as a Docker container or a .deb package on your own server, with no dependency on a cloud provider. Sign-in is passwordless via WebAuthn.

iOS

My own apps in Swift and SwiftUI, from a mood journal to trip planning for a motorhome. They run locally or against a self-hosted server.

Contact

Get in touch

Questions about the apps or projects are welcome by email. I am also on Mastodon.

Send an email Mastodon Buy Me a Coffee