Modernization of a legacy codebase by code modularization, cleanup and refactoring using PHPStan, CodeSniffer,
and Rector. Implementation of client management functionality, modularizing and integrating within the legacy
codebase (TypeScript, React). Upgrade PHP 7.4 codebase to PHP 8.2, ensuring smooth upgrades of incompatible
dependencies.

Integration of a 3rd-party PLM system into legacy systems (FashionXL) via XML/SOAP. Development of an
event-driven architecture built on Kafka, aggregating data into an in-house PIM system. Adaptation of AWS CDK
(Cloud Development Kit) into the team to facilitate architecturing data product pipelines across teams, defined in
code. Building data contracts validated by JSON Schema to facilitate JSON-based REST communication between
microservices

Support the team with migration to AWS servers (S3, EC2), infrastructure growth by leveraging an in-house Event
Sourcing implementation.
Runtime profiling and optimization by reducing SQL query complexity and/or offloading workloads to the DB.

Greenfield implementation of a marketplace for candidate referrals used by 500+ companies.
Optimized User Exprience by involving Server-Side Rendering, keeping the TTFB response rates <150ms, and
leveraging HTMX for user-interactive AJAX requests, keeping the added TTI (Time To Interactive) below 20ms.
DevOps: Established a CI/CD pipeline based on industry-standard best practices, allowing for up to 10 zero-downtime
deployments to production per hour, staging and QA environments.
Unit Testing and fully automated browser-based functional testing triggered via code commits by the team using GitLab
CI minimizes human error during development. Database Schema migrations using Flyway. Hybrid cloud/bare-metal
server infrastructure. (AWS, Google Cloud, Arch Linux natively on on-premise servers).
Image delivery and transformation via headless Inkscape and Cloudinary CDN API.
Scraping of 20 different ATS (Applicant Tracking System) providers in addition to API integrations for job listing
imports and candidate exports. Data Mining and extraction from crawled job postings and candidate profiles. Algorithm
design to find the best-performing overlap of auto-extracted vacancy requirements and candidate skills.
?PHP, Symfony, PostgreSQL, Clojure, OpenJDK, GraalVM, Intercooler.js.

Shopware upgrade and maintenance, TLS certificate setup, plugin and theme upgrades and customizations.

Migrate old PHP4/5 codebase of a costume rental store to PHP7; audit code for secruity vulnerabilities and fix those.
Migrate code to a Service-Oriented Architecture (SOA) using the Mikado Technique.
Add End-to-End tests and unit tests for the legacy codebase using Codeception. Add custom functionality as customer
desires. Ongoing maintenance and hosting.

Upgrade a Shopware plugin code base in order to make it run on the upgraded Shopware 5.4.

Led a growing team during a progressive modernization of a Wordpress-based site infrastructure to a microservice
architecture based on Symfony 3, facilitating a separate frontend in Vue.js. TDD coaching and process implementation.
Architecture design and implementation.
Optimized database schemata and query infrastructure to facilitate 3mln. visits / day. Integration of Cloudinary image
delivery CDN. API integration to E-Commerce partners connexity.com, guenstiger.de, billiger.de. Amazon
MWS/AWS API integration. Research and implementation of reliable crawling/scraping algorithms for Amazon.

Greenfield implementation of an E-Commerce flat share booking site. Development of an administrative back office for
customer and property management via Sonata Admin Bundle and AdminLTE. Migration of features from a legacy
MVP developed in Zend Framework 2, MySQL, and Drupal to a modular, Symfony-based microservice architecture.
Integrated the payment providers Paymill and Adyen. PHP, JavaScript, REST API. Developed and documented a
RESTful public-facing API for B2B partners.

Implementation of a recommendation algorithm based on customer?s shopping history. Memory usage reduction for
CSV and XML file exports by 64%, as well as other significant optimizations. Design and implementation of an
algorithm to automate voucher code generation and validation.

Introduced a CSS framework based on Object-Oriented CSS for a web site relaunch in 2012, reducing file size of
included CSS files over 30% and significantly slowed growth of the necessary CSS instructions while the project grew.
Developed a PHP based adapter solution for a legacy authentication system (REST/JSON ? SOAP/XML) for the
publisher?s ePaper software.
Co-developed and maintained templates and plugins for fCMS, a 3rd-party CMS specifically built for the publishing
industry, in HTML5+CSS3, PHP and JavaScript.
Developed Wordpress plugins and themes for several of the publisher?s long-form storytelling projects (storytelling.swp.de/spielraum, storytelling.swp.de/mauerfall, storytelling.swp.de/karlsplatz) and contributed to existing
open-source plugins ([1], [2]); provided coaching and support for the journalists.
Initiated Unit Testing and Test Driven Development with PHPUnit, XDebug, and browser test automation via
NightmareJS/PhantomJS
Introduced graceful degradation for swp.de to optimize rendering in legacy browsers (Internet Explorer 8 and 9)
Introduced git to retire CVS.