Case examples & references

Here you'll find a selection of case examples and results from projects. The examples describe typical problems, approach, and results.

Retail media platform & integrations for self-service advertising

Initial situation

For a modern retail media platform, legacy systems had to be replaced and the technical foundation for a scalable self-service solution created. Integrations and data flows had to run reliably and be production-ready.

Goal

Build a stable, extensible platform foundation so advertisers can reliably manage campaigns, audiences, and delivery on their own.

Approach

  • Designed and built microservices with Kotlin/Spring Boot
  • Implemented and maintained REST APIs for internal and external systems
  • Integrated Kevel to serve ads dynamically
  • Built data workflows with Apache Airflow and managed database changes with Liquibase
  • Team collaboration: quick ramp-up, clean handoffs, documented decisions

Result

  • Scalable foundation for the new self-service platform
  • Reliable integrations and robust data flows
  • Traceable deployments and stable operations
  • Faster delivery of advertising and campaign requirements

Technology (excerpt)

  • Kotlin, Spring Boot
  • Microservices, REST APIs
  • AWS S3, Elasticsearch
  • Apache Airflow
  • MySQL, Liquibase
  • Docker, Kubernetes, Terraform
  • Grafana, Kibana
  • GitHub Actions, Jenkins

Role

Senior Engineer as part of a team (hands-on delivery)

Customer service web application at a large direct bank

Initial situation

Phone-based customer service needed a central web application for financial services. At the same time, regulatory and technical changes had to be implemented continuously without jeopardizing stability.

Goal

Deliver new features and operate the application reliably, maintainably, and compliantly.

Approach

  • Extended Java applications and delivered upgrades (Java/JEE, Spring, Hibernate, SQL)
  • Adapted to regulatory and technical requirements with Spring and Wicket
  • Ensured stability through bug fixes and targeted refactorings
  • Introduced/expanded automated tests for quality assurance
  • Integrated third-party systems via REST and web services; supported operations, builds, deployments, and DBs

Result

  • Reliable execution of customer service processes
  • Faster adjustments for regulatory changes
  • More stable operations through tests and bug fixes
  • Less friction in build/deploy workflows

Technology (excerpt)

  • Java, JEE, Spring
  • Hibernate, Oracle DB, SQL
  • Wicket
  • REST APIs, SOAP/web services
  • Build/Deploy: Maven, Jenkins, Azure Pipelines
  • Automated tests
  • Database management

Role

Senior Engineer as part of a team (hands-on)

App modernization & delivery improvement at an established digital health company (cycle-tracking app, millions of users/month)

Initial situation

A large mobile app grown over years with high quality expectations. Modernization and feature development had to run in parallel without losing users or destabilizing releases.

Goal

Deliver new features while improving modernization, quality, and the release process.

Approach

  • Modernized existing app structures and introduced new components
  • Implemented UI modernization and reduced technical debt
  • Analyzed performance/error patterns and improved them
  • Optimized CI/CD and release flows pragmatically
  • Supported backend-adjacent tasks when needed to deliver end-to-end cleanly

Result

  • Improved maintainability and faster delivery of new requirements
  • More stable releases and clearer error analysis
  • Modernized architecture aligned with current standards
  • More stable releases and better error analysis even under high usage/scale

Technology (excerpt)

  • iOS: Swift, SwiftUI, UIKit, async/await
  • CI/CD: fastlane, GitHub Actions
  • Observability/debugging: crash/logging workflows (tool-agnostic)
  • Optional backend parts: Kotlin/Java, REST APIs (when present)

Role

Senior Engineer (mobile, hands-on)

CRM controls portal access, prices, and features

Initial situation

Portal access and visibility of prices/features should be strictly tied to whether a contact in the CRM is approved.

Goal

Only approved contacts get access; the portal behaves consistently based on CRM status and attributes.

Approach

  • Hard gate: registration/login tied to CRM status
  • Synchronized attributes/roles from the CRM into the identity solution
  • Created leads in the CRM from the registration process when needed
  • Captured consent during registration and wrote it back to the CRM

Result

  • Clear approval process for sales
  • Consistent feature control based on CRM data
  • Significantly less support and clarification effort around access
  • Better traceability of why someone has access or not

Technology (excerpt)

  • Keycloak, OIDC/OAuth2
  • Salesforce via REST APIs

Role

Implementation and technical concept of the interface between Keycloak and Salesforce

AI workflows: automation, data transformation, and knowledge access for less manual work

Initial situation

Recurring processes contain many unstructured inputs and media breaks, such as emails, free text, documents, and attachments. Information must be manually read, summarized, translated, or transferred into target systems. Without a clean data foundation, errors, follow-up questions, and rework emerge.

Goal

Automate recurring work steps while ensuring that data is valid, traceable, and usable in the target system. AI should support where it measurably relieves effort, without destabilizing the process.

Approach

  • Data foundation: normalize, validate, and transform inputs into a clear schema (mapping and transformation)
  • AI building blocks: extraction, classification, summarization, and translation with structured outputs so results can be processed further
  • Optional agent-based workflow: orchestrate multiple steps and invoke defined tools via interfaces, with clear boundaries and review step
  • Search and knowledge access: index content, ensure source references and consider permissions so answers remain traceable
  • Quality and operations: logs, evaluation, cost control, and monitoring so the workflow stays stable and can be improved iteratively

Result

  • Less manual work through automated preparation and structured results
  • More consistent quality through validation, clear rules, and traceable logs
  • Faster processing through AI support in classification, translation, and search
  • A process that remains reproducible and can be improved iteratively

Technology (excerpt)

  • AI and LLM, depending on requirements frontier models or open-source models on-premise
  • Structured outputs (e.g., JSON schema), tool use, and function calling
  • Retrieval, embeddings, and indexing for search and knowledge access
  • Validation, mapping, and transformation as robust pre- and post-processing
  • Logging, evaluation, and monitoring
  • n8n as workflow orchestration and integration layer, combined with custom components where needed

Role

Concept and implementation, from prototype to integration into existing workflows

Testimonials

Over the course of my career, I have worked both as a full-time software engineer and as an independent consultant for various organizations. These experiences gave me the opportunity to collaborate with many talented and great people. Here are a few testimonials from them:

  • Eliamo Touma
    Talent Specialist Lead

    “I've had the pleasure of working with Markus Krischke across two demanding projects—first in the banking sector and currently in the e-commerce domain. Markus is an exceptionally skilled Senior Backend Developer with over two decades of experience in software engineering, particularly in Java and Kotlin.

    What sets Markus apart is his ability to tackle complex technical challenges with clarity and precision. During our collaboration at ING, he played a key role in enhancing a critical web application used for internal banking operations, including account transactions, fraud case handling, and credit card management. His deep expertise in Spring Boot, Kafka, and microservices architecture was instrumental in delivering scalable and secure solutions.

    In our current e-commerce project, Markus continues to demonstrate his versatility. He develops robust backend features within a microservices setup, optimizes CI/CD pipelines, and ensures seamless service communication. His consulting skills are especially noteworthy—he excels at understanding business requirements, engaging stakeholders, and translating needs into strategic technical solutions.

    Beyond his technical capabilities, Markus brings outstanding soft skills to the table. He is structured, communicative, and highly proactive in agile environments. His experience working in international, remote teams makes him a reliable and collaborative team member.

    Markus is not only a top-tier developer but also a strategic thinker and trusted advisor. I wholeheartedly recommend him and look forward to future opportunities to work together.”

  • Gohar Gasparyan
    Senior Engineering Manager

    “I worked closely with Markus at Clue for a year and was lucky to be his manager. Markus is an exceptionally skilled senior iOS engineer. His work is clean, efficient and fast, always informed with best practices and lots of attention to detail.He is very passionate about iOS latest and greatest and besides can also help put on backend when needed.

    You can rely on him breaking down any complex task and handle on his own. He has been a great mentor for other teammates, reviewing and consulting them, but at the same time not imposing his views and letting them drive their own growth. Markus will always give an honest, unfiltered feedback and that has been of a great help for the team. I would highly recommend working with Markus.”

  • Emeline Cordat
    Senior Product Owner / Teamlead Product Management

    “I had the chance to work with Markus on various Apple applications (iOS mobile, tablet, and tvOS). Among other things, I shared with him a particularly exciting project: creating an Apple TV application from scratch. As a Product Owner, collaborating with Markus was an incredibly enriching and enjoyable experience.

    Markus is an exceptional developer, highly reliable, and truly passionate about delivering the best possible product to users. He doesn't just implement features: he puts himself in the users' shoes, constantly strives to understand their needs, and goes beyond expectations to provide tailored, relevant, and pragmatic solutions. He truly cares about improving the product, values good design, and knows how to identify and recommend quick wins.

    Beyond his impressive technical skills, Markus is also an exemplary colleague. His calm demeanor, total dedication to the project, efficiency, and ability to collaborate with team members make him a real cornerstone. He is a true team player - always ready to listen, share ideas, push the project in the right direction, and actively contribute to ensuring the team achieves its goals.

    Our collaboration was a real success overall, and in particular during the development of the search function for the Apple TV app, where we worked closely as a duo. Working with Markus was a genuine pleasure for me, and I can warmly recommend him to any team looking for a talented, pragmatic, passionate, and dedicated developer. He was a key contributor to the success of our Apple applications, and I am confident that he will continue to excel in any project he takes on, whether inside or outside the Apple world!”
    (Translated from FR)

  • Christian Storch
    Chief Technology Officer (CTO)

    “I had the pleasure of working with Markus and can confidently say he is an outstanding professional who consistently exceeds expectations. Proactive and forward-thinking, Markus tackles challenges head-on and drives initiatives independently, making a significant impact across teams.

    His expertise in mobile application architecture is remarkable. He led the development of a unified codebase for multiple brands and Apple platforms, enhancing our processes and improving scalability.

    What sets Markus apart is his ability to innovate. The "Magic Login" feature is a prime example; he conceived, designed, and guided it through patent filing, implementation, and cross-team adoption, showcasing his technical skills and collaborative spirit.

    Markus is a true leader who fosters innovation and delivers impactful results. I wholeheartedly endorse him for any role that requires expertise and leadership in mobile application development or technical architecture.”

  • Florian Taufer
    Founder, Product Owner

    “Markus was an integral part of our small team that developed the multilingual software PINO-LA. This software enables efficient management of ETIM data, the global standard for product descriptions in the electrical industry.

    In his role as a software developer, Markus not only demonstrated his extensive programming expertise impressively, but also familiarized himself remarkably quickly with the complex subject matter of ETIM data. His commitment to also diving into the domain-specific details was a major advantage for the project.

    I would particularly like to highlight his strong understanding of the business requirements and his ability to contribute his own excellent ideas and solution proposals. This initiative and his analytical mindset significantly contributed to the success of the project.

    Working with Markus was always characterized by trust and a positive working atmosphere. I greatly valued his professional attitude, his reliability, and his ability to work effectively as part of a team.”
    (Translated from DE)