Project Reference
 - Telephone systems for thousands of business customers – 100 % cloud


Our Customer:
Market leader in telecommunications

Our client is a multi-billion heavyweight in the telecommunications industry, with millions of private and business customers. By relying on promising new technologies and the constant evolution of their products, their existing business models stay fit for the future without compromising the development of new options. This flexibility would not be possible without staying up to date in the field – especially in terms of software development.

Starting Point

Our client was looking for a reliable and competent partner for a complex backend project. It offers a modern product for virtual IP telephone systems (cloud PBX), with in-house developed user interfaces. Those user interfaces had to be connected to other internal systems and to the cloud-based telephony platform. For this purpose, a customized software had to be developed.

The client’s cloud PBX product is a modern virtual IP telephone system for business customers combining internet, telephony, and a virtual telephone system. It is a lightweight flexible solution which reduces investment and maintenance costs by making physical telephone systems on premises unnecessary, while also setting an ideal foundation for mobile work. End users can place and receive phone calls via a desktop application, office phones and smartphones, and they can easily manage their own settings and configurations via a user interface. The product has been successfully in use for several years – from small businesses to call centres.

The technology behind the telephony was developed by a different partner and is operated in our client’s own cloud, while the user-friendly web interfaces and mobile apps for configuration and adjustment of the virtual telephone systems were designed and developed by our client in-house. What was missing was the core of this business-critical platform: software that would reliably enable communication between the two by implementing the entries made in the user interface as changes in the telephony software. Additionally, the product had to be integrated with several business processes with other systems of our client, for example CRM, billing and data warehouses.

The Project


Analysis, development, DevOps, automated acceptance tests, maintenance


Scrum, SAFe, test-driven development, continuous integration and delivery


Java, Spring, JPA/Hibernate, Gradle, Cucumber, SonarQube, Gatling, MariaDB, H2 Memory DB, SOAP, REST, openAPI, Elasticsearch, Logstash, Graylog


This is where cronn came in: We have been involved in the backend’s development from the beginning. Our responsibilities include conception, development and advancement of the backend that connects the user frontends with the actual virtual telephony technology. Today, the project contains millions of lines of code – each one automatically tested. The system maps all processes, implements the desired adjustments in the telephony software and provides feedback to the user via automated emails. Furthermore, our team developed interfaces connecting our client’s specialist departments – for example customer support, accounts receivable department, CRM or the company's own data warehouse – allowing them all to exchange data and information with the backend we created.

In this way, the system optimises our partner's level of automation towards the end customer and increases internal efficiency. For example, customers can add and configure product options in user interfaces, which is then automatically considered in the subsequent invoicing. All relevant business and telephony logics therefore had to be mapped in the backend, for which cronn had to gain a deep understanding of many of the customer's systems and processes. Despite the complexity and size, the entire system must always run stably – a failure of the productive system would lead to disruptions for thousands of business customers.

By now, we have been involved in the constant further development of the product for years. Due to our experience in this complex project, the close cooperation with our client and their other partners, as well as our deep understanding of many of our client’s systems and processes that we have gained over the time, our team is still in high demand – from the software specification to the implementation of new features.

The cronn project team comprises more than a dozen software developers, test automation engineers, DevOps engineers, project managers and analysts, all of whom value the opportunity to make a fundamental contribution to a complex, mission-critical project for our customer in close partnership. The system developed by cronn is not only the heart of our client’s product – it is also a matter close to our hearts.

Customer Advantage

From the very beginning our customer benefited from the open and trusting cooperation. By using proven open source technologies, costs are kept low and quality high, and the project always remains transparent for the customer. In addition, the project is scalable through cronn as a service provider and the customer can flexibly plan the use of resources as needed. The cronn team has relied on our proven stack of common open source technologies in the project since the beginning. This means that the technologies used remain stable and up-to-date over a long period of time.

With such a system, special attention is also paid to extensive testing. Our approach to test-driven software development, ensures that only valid code makes it into the production system, since any error could have an impact on the telecommunications infrastructure of thousands of business customers.

Our team not only leaves no line of code untested thanks to test-driven software development, but also continuously carries out tens of thousands of unit, integration and acceptance tests, which are automatically executed with every further development. This ensures that new features function and work smoothly with all components of the system before they go live. This is done on test servers or using simulators specially developed by our team. The cronn team has fully automated the test landscape from the beginning, which leads to a high level of efficiency. This way, we guarantee our customer high software quality, fast development and flexibility for the project.

cronn Pluspoint

Longstanding partnership

Project involvement from the development phase in 2014 until today

complete project team

Autonomous team with lead, project manager, analysts, developers and testers

Intensive testing

Tens of thousands of automated tests to ensure highest quality


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