The architecture of otto.de is based on the concept of vertical decomposition: the whole system is vertically split into several loosely coupled applications. Every „vertical“ is responsible for a single business domain such as „Order“, „Search & Navigation“, „Product“, etc. It has its own presentation layer, persistence layer and a separate database. From the development perspective, every vertical is implemented by exactly one team and no code is shared between the different systems. We have already described the details of this architecture in an article in  OBJEKTspektrum (German), a different blog post (German) and at conferences like QCon (English).

Vertical Decomposition
Vertical Decomposition

For some time, a different approach to decompose large systems is becoming more and more popular: microservices. What are the similarities and differences of both kinds of architectures and how is it possible to get the best of both? This is what I want to discuss in this text.

This is part two of my roundup of  EuroClojure 2014. If you missed the first part, find it here.

Day two started with the keynote by David Nolen about Invention, Innovation & ClojureScript. After some interesting discussion on the difference between invention and innovation, he talked about the history of clojurescript, a clojure implementation that does not target the jvm but javascript as a runtime environment. It was released 3 years ago and since then undergoes constant innovation. To date, the innovations come from 81 different contributors. Examples for contributed innovations are persistent immutable datastructures and source maps, which are very useful for debugging clojurescript. David introduced the basics on react.js and then of om. Om is a clojurescript library on top of react.js. It adds a key ingredient to react: Immutability. By having an immutable global application state, communication between components becomes feasible without any of those crazy interactions, that make classical user interface development so hard. As an example David  showed Goya, a pixel editor for the browser. Due to clojurescript’s persistent datastructures it features undo/redo of a virtually unlimited number of steps with little to no performance impact at all. David finished with an outlook on clojurescript 1.0. Among the goals is better code sharing between clojure and clojurescript.

view from the conference center
The beautiful view from the conference centre.

Last week I attended the EuroClojure conference 2014. It was a truly fantastic conference in the beautiful city of Kraków. While the big conferences in the US attract thousands of participants, this one was rather cosy with some 300 participants. As a very good side effect of this, the conference was single tracked. So I missed none of the great talks.

If you do not know clojure by now, let me start with a very short primer: Clojure is a modern, functional programming language targeting the java virtual machine. It is a lisp dialect, designed for concurrency, performance and code that is easy to understand and thus easy to reason about. One of the most outstanding features of clojure is its immutable, persistent datastructures directly built into the language. With clojurescript there also exists a version of clojure targeting javascript rather than the jvm as a runtime.