Design Pattern

Reactive streams address a fundamental problem of modern systems: Producers (sensors, services, user events) deliver data at an unpredictable rate , while consumers (persistence, UI, analytics) can only process data at a limited speed. Without a flow control model , backlogs, storage pressure, and ultimately outages occur.

1. Introduction and motivation # The observer pattern is one of the basic design patterns of software development and is traditionally used to decouple state changes and process them. Its origins lie in the development of graphical user interfaces, where a shift in the data model required synchronising several views immediately, without a direct link between these views. This pattern quickly established itself as the standard solution to promote loosely coupled architectures.

A URL shortener seems harmless – but if implemented incorrectly, it opens the door to phishing, enumeration, and data leakage. In this first part, I’ll explore the theoretical and security-relevant fundamentals of a URL shortener in Java – without any frameworks, but with a focus on entropy, collision tolerance, rate limiting, validity logic, and digital responsibility. The second part covers the complete implementation: modular, transparent, and as secure as possible.

The Bird-Eye View # A Compensating Transaction Pattern is a technique used to ensure consistency when multiple steps are involved in a process, and some steps may fail. It essentially consists in having “undo” transactions for each successful step, so if something goes wrong later on, you can reverse the changes made earlier and maintain data integrity.

Builder-Pattern # The book from the “gang of four” is part of the essential reading in just about every computer science branch. The basic patterns are described and grouped to get a good start on the topic of design patterns. But how does it look later in use? Here we will take a closer look at one pattern and expand it.