Sebastian Wessel

Implementation of microservices in Typescript in a cloud-based infrastructure for the generation of various documents and output formats.

RabbitMQ was used for communication between individual microservices and MSSql as data storage.

The challenge here was in particular the need to handle millions of document orders with limited resources.

Orders for document creation were bundled and transferred to an external service via Rest-API.

The external service, in turn, could only process a limited number of orders simultaneously and their processing was very time-consuming, so that corresponding waiting loop mechanisms were necessary, which also function reliably across multiple service instances (parallel processing).

Furthermore, generated documents had to be processed accordingly and delivered to various other external services.

Unfortunately, the project had to be terminated prematurely by the client due to the ECJ ruling on the German passenger car toll.

Due to the experience in previous projects with the Node.js connection to the Eventstore (eventstore.org), the idea arose to create our own client library that meets modern needs.

Particular attention was paid to Test Driven Development, Clean Code and documentation.

This makes it possible for users to create easy-to-understand source code in their own applications. This is supported not only by the use and provision of async/await functions, but also by the naming of methods and (alias) functions.

The implementation was done in Typescript in order to be able to use the advantages of typing and, on the other hand, to ensure easy use in both plain Javascript and Typescript.

In order to automate the process as much as possible, a CI/CD pipeline was set up, which automatically runs tests in corresponding Docker environments, creates code coverage and sends it to third-party providers and, if necessary, creates the client library and transfers it to the NPM repository.

The source code and documentation are freely available at:

https://github.com/sebastianwessel/eventstore-ts-client

Implementation of the central functions of the overall system from conception to implementation to automated testing.

For backend development, Node.js-based microservices were implemented within a Microsoft Azure-based cloud infrastructure. The following things played a prominent role:

The connection to external loyalty providers via API and web scraping for data exchange and the provision of data via REST-API for mobile clients. Furthermore, the complete architecture is based on CQRS/Event-Driven-Design and Eventstore was used as data storage instead of a classic database.

Since this project is a project within the financial industry and involves sensitive user data, an above-average importance was given to the topics of security, audit, testing, etc.

Both the development, testing and operation of the service were implemented on the basis of Docker containers and their management with Kubernetes.

In this project, the complete process from the basic idea to the publicly available product was accompanied and shaped.