Johannes Erchen - Senior Application Developer

Recommended expert

Hamburg, Germany

Experience

Sep 2022 - Present

3 years 5 months

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Libri GmbH

Operation and further development of the inventory system for booksellers (Quimus). It is an in-house development by Libri that is sold to customers as Software as a Service. The software is developed in an agile way by two developer teams (about 5 developers each). The software consists of around 25 Java microservices that mainly communicate via messaging and share a common Angular frontend. The application runs on Kubernetes in AWS.
Technologies used: Java 17 & 21, Spring Boot 2 & 3, Hibernate, MySQL, Spring Cloud AWS, Lombok, AWS SQS, AWS SNS, AWS RDS, AWS S3, DynamoDB, Kubernetes, Docker, OpenSearch, Hibernate Search, Liquibase, Gradle, Terraform, Helm, GitLab CI, Keycloak OAuth2, TypeScript, Angular
My focus until December 2023: Connecting additional POS systems to the inventory system. Connecting the data warehouse for report display. Extending existing features (goods receipts, invoicing, item management, ...). Operations and DevOps tasks.
Focus from January 2024: Extracting the product search from the inventory system into a global service to use in other applications. Integrating the product search into the booksellers' online shops (also run by Libri). Importing and providing digital items in the product search.

Nov 2021 - Aug 2022

10 months

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EOS Technology Solutions GmbH

Agile development of the B2B portal for coordination between EOS and clients. Integrating additional systems into the existing product.
Backend technologies: Java 17, Kotlin, Spring Boot, Spring Cloud Gateway, Lombok, GraphQL, REST, RabbitMQ, Gradle, Oracle, Liquibase, Docker, Jib, Kubernetes, Jenkins, GitLab CI, JUnit 5, Mockito, WireMock
Frontend technologies: TypeScript, React, Redux, Apollo, Jest, TestCafe.

Apr 2021 - May 2022

1 year 2 months

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Brunata-Metrona GmbH

Complete redevelopment of several microservices for receiving and processing measurement data for heating cost billing.
Support in architecture and project setup.
Technologies used: Java 17, Spring Boot, MongoDB, Microsoft SQL Server, Liquibase, Docker, Jib, Lombok, Gradle, JUnit 5, AssertJ, Mockito, WireMock, Jenkins.

Jan 2021 - Jun 2021

6 months

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KONMATIK GmbH

Initial support in setting up a project and then support with a few hours per week.
Training of employees.
Technologies used: Java 11, Spring Boot, Lombok, Vaadin, GitLab CI, Maven, JUnit 5, Mockito, MariaDB, Liquibase, Docker, Jib.

Jan 2021 - Mar 2021

3 months

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edict egaming GmbH

Agile development of an online casino backend.
Support in splitting it into a microservice architecture.
Technologies used: Java EE, Quarkus, Lombok, Maven, JAX-RS, PostgreSQL, Mockito, TestNG, Payara, Helm, Kubernetes.
The project was abandoned by the parent company at the end of February.

Apr 2019 - Dec 2020

1 year 9 months

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EOS Technology Solutions GmbH

same project since 11/2021

May 2018 - Sep 2019

1 year 5 months

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moebel.de Einrichten & Wohnen AG

Complete redevelopment of the entire portal with Spring Boot microservices on AWS.
Technologies used: Java 11, Spring Boot, JAX-RS, Lombok, Maven, Algolia, MongoDB, mongobee, Docker, AWS EC2, AWS SQS, CloudFormation, GitLab CI, DataDog, Thymeleaf, FluentLenium, REST, JUnit 4, Mockito, WireMock.

Jul 2017 - Jul 2018

1 year 1 month

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Cubic Transportation Systems (Deutschland) GmbH

Developed the Java backend of a React Native mobile ticketing app for public transport for the US market.
Technologies used: Java 8, Spring Boot, Lombok, Maven, ELK, PostgreSQL, Docker, Netflix Zuul, GitLab CI, DataDog, Jenkins, JUnit, Mockito.

Mar 2017 - Jul 2017

5 months

Senior Application Developer

Interone GmbH

Architecture, consulting, and coaching for building a microservice platform for a large energy company.
Consulting and implementation of continuous delivery pipelines for various clients.
Technologies used: Java, Spring Boot, Lombok, Maven, Amazon AWS, GitLab CI, Docker, JUnit, Mockito.

Apr 2016 - Feb 2017

11 months

Senior Software Engineer

Kühne + Nagel (AG & Co.) KG

Developed a microservice application for selling logistics services over the web.
Agile software development with Kanban.
Technologies used: Java, Spring Boot, Oracle, GWT, AngularJS, jQuery, RabbitMQ, SOAP, Ansible, ELK, JUnit 4, Mockito, Selenium, Gradle, Git, Tomcat, HAProxy, Jenkins.

Feb 2014 - Mar 2016

2 years 2 months

Senior Consultant

Tallence GmbH

Main contact for clients WeltN24 GmbH and SPD.
N24: Used CoreMedia CMS as the central system to control all delivery channels: web, mobile, apps, info screens (e.g., at airports).
Provided coaching and architecture for a sub-project of stern.de at Gruner + Jahr.
Other technologies used: Spring, MySQL, PostgreSQL, MongoDB, ElasticSearch, Maven, Git, SVN, Varnish, jQuery, Apache Web server, Tomcat, IntelliJ IDEA.

Nov 2010 - Jan 2014

3 years 3 months

Senior Application Developer

Interone GmbH

Programming content management systems in Java with CoreMedia or Spring 3, as well as developing Android apps for clients: O2 Telefónica, N24, BMW, Affinion International.
Provided technical guidance to developer teams made up of junior application developers and external developers.
Further development of the community platform “o2more”.
Relaunch of the N24 website.
Development of several Android apps for savings banks.
Other technologies used: Maven, SVN, Hibernate, Oracle, MySQL, Varnish, jQuery, Apache Web server, Tomcat, Eclipse, IntelliJ IDEA.

Oct 2008 - Oct 2010

2 years 1 month

System Engineer

hamburg.de GmbH & Co. KG

Managed the CoreMedia system for hamburg.de.
Developed new features.
Optimized and maintained operations.
Technologies: Java, CoreMedia, Spring, Hibernate, Oracle, Maven, SVN.
Coordinated with service providers and the City of Hamburg.

Apr 2008 - Sep 2008

6 months

Software Developer

mindworks GmbH

Developed various CMS projects in PHP and MySQL.
Mainly responsible for the development and maintenance of mopo.de.
Other projects included ftd.de, stern.de, and hinzundkunzt.de.

Sep 2006 - Mar 2008

1 year 7 months

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Moorbek Computer Systeme GmbH

Created a Java application for automatic ordering and provisioning of domains.
Built a frontend in PHP.
Used MySQL as the database.

Jan 2004 - Mar 2007

3 years 3 months

Student assistant in technical operations

hamburg.de GmbH & Co. KG

Developed and maintained the web controlling tool in PHP and MySQL.

Jan 2001 - Dec 2006

6 years

Freelance work

Rechtsanwälte Mierau & Domscheit

Provided technical support for a law firm with about 10 employees.

Summary

20 years of experience developing web applications with a focus on the backend
Over 15 years of professional experience in Java/Spring development
Experience with common frontend technologies (TypeScript, React, Angular, jQuery)
Clean Code and TDD are not foreign to me, but my preferred approach
Over 10 years of experience in agile software development (Scrum & Kanban)
Extensive DevOps experience (Amazon AWS, GitLab, Linux, Docker, Kubernetes)
Extensive experience with standard development tools (IntelliJ IDEA, Jira, Confluence, GitLab, Jenkins, SonarQube)

Languages

German

Native

English

Advanced

Education

Oct 2004 - Mar 2007

Physikalisch Technische Lehranstalt Wedel

Technical college entrance diploma, state-certified technical assistant for computer science, focus on business informatics · Computer Science · Wedel, Germany

Oct 2001 - Jun 2003

Ernst Barlach Schule Wedel

Secondary school diploma · Wedel, Germany

Oct 1996 - Jun 2001

Johann Rist Gymnasium Wedel

Wedel, Germany

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Libri GmbH

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edict egaming GmbH

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moebel.de Einrichten & Wohnen AG

Cubic Transportation Systems (Deutschland) GmbH

Senior Application Developer

Interone GmbH

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Kühne + Nagel (AG & Co.) KG

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Tallence GmbH

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Interone GmbH

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hamburg.de GmbH & Co. KG

Software Developer

mindworks GmbH

Moorbek Computer Systeme GmbH

Student assistant in technical operations

hamburg.de GmbH & Co. KG

Freelance work

Rechtsanwälte Mierau & Domscheit

Summary

Languages

Education

Physikalisch Technische Lehranstalt Wedel

Technical college entrance diploma, state-certified technical assistant for computer science, focus on business informatics · Computer Science · Wedel, Germany

Ernst Barlach Schule Wedel

Secondary school diploma · Wedel, Germany

Johann Rist Gymnasium Wedel

Wedel, Germany

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