REST API Experts in Hamburg

As a Council Member at GLG (Gerson Lehrman Group), the world’s leading expert network, I provide organizations, investment firms, and consulting companies with expert discussions on demand – wherever specialized knowledge in information security, IT governance, and regulatory compliance is needed.

My assessments are based on many years of practical experience in highly regulated industries: from building and implementing information security management systems (ISMS according to ISO 27001), IT risk and vulnerability management, and business continuity (ISO 22301) to the practical implementation of European regulations such as DORA, NIS2, BAIT, and the Cyber Resilience Act (CRA).

The cooperation is project- and discussion-based. I provide decision-makers with a practical perspective gained from real-world experience on cyber risks, security governance, and operational resilience – exactly when it is needed.

• Designed and moderated a NIS2 preparation workshop for RAS Reinhardt Maschinenbau GmbH and its IT service provider Catuno GmbH. Together with executive management and IT leadership, the current status was assessed, an initial GAP analysis was conducted and areas for action were prioritized based on ISO 27001.
• Developed an ISO-27001-based regulatory framework (ISMS) for NIS2 compliance, including a structured current/target GAP analysis, targeted improvement of the security maturity level and preparation of the organization for NIS2 audit readiness.

• Consulting, training and coaching in the financial sector on strategy, organization and IT topics

• MorgenFund: Advising the operator of a fund platform on software selection for a sub-ledger "Cash Accounts" based on virtual IBANs (VIBAN)

• Structuring requirements, market screening, preparing RfIs, communicating with vendors and conducting the selection process

• UniCredit/HypoVereinsbank: Workstream Lead "Booking and Customer Reporting" in the payment transformation project "PULS"

• Business analysis, preparing business requirements and coordinating the solution items as part of the functional specification with the bank's IT service providers

• Business analysis of SEPA CT and SWIFT MX (.camt-, .pain- and .pacs- formats), change management, team leadership for a virtual team of fifteen line experts and stakeholder management

• equensWorldline Germany: Program management for three projects of the SWIFT Service Bureau (CBPR+, ESMIG and Euro1Step1 migration) as part of the SWIFT MX migration

• Managing individual project leads with regard to cross-project goals and requirements; reporting to internal and external committees and stakeholders; coordination with dependent projects and programs

• Project management/PMO: Interim project management, deputizing for project leads, resource planning, budget and cost management, general PMO activities

• Building a data integration platform for high, medium, and low voltage assets for contextual analysis of time series with master data from the SCADA control system (IEC 60870 104), INIS, and SAP.
• Responsibility for the architecture and implementation of the solution, as well as sparring partner for the Product Owner.
• Use of Kotlin, Spring Boot, Maven, TimescaleDB, PostgreSQL, liquibase, Elements IoT, Docker, Kubernetes, Grafana, Python, jupyter, and various API gateways.

• Assumed responsibility for backend architecture and technical strategy, planning and leading the platform's evolution in close collaboration with the CTO
• Simultaneously drove the development of new features for the housing and tenant management platform, balancing high-level architectural design with hands-on implementation
• Utilized AI-assisted workflows (with tools such as Claude Code, Codex, Cursor) and worked on AI-based features (with tools such as N8N, Mastra, ElevenLabs)

Technologies: Node.js, TypeScript, React.js, Next.js, PostgreSQL, Google Cloud, Docker, Kubernetes

Co-founded a software agency building custom web and cross-platform products. I owned the technical decisions across the whole portfolio and led 12 people, while carrying delivery planning, process and client relationships for 11 clients across 3 industries.

• Technical leadership: owned the technical decisions for the codebase across every project — stack, architecture, code conventions and the tooling the team worked with — and led the developers on how work got built through code reviews, pair programming and mentoring across a team ranging from junior to senior, keeping the codebase coherent as the portfolio and the team grew

• Delivery planning against the financial plan: built the company's financial plan and derived from it the billable hours each developer had to reach per month and the hours each project could absorb to stay within budget; planned capacity and scope against those figures and negotiated budgets and delivery dates directly with clients

• Client ownership: technical contact across the portfolio — requirements gathering and prioritisation, scoping and estimates, timeline communication, budget negotiation, and consistent transparency throughout delivery

• Team and people: owned the hiring and interview process end to end and took responsibility for offboarding where it was needed; designed an onboarding that got new developers productive within 1–2 days; cleared blockers daily and kept a close eye on where effort was creating value and where it was not

• Process ownership: consolidated a micro-service landscape spread over 15+ repositories into a single monorepo, cutting backend development time by ~40% and simplifying releases for 6 engineers; set up deployment pipelines with GitHub Actions and GitLab CI; ran retrospectives and turned the feedback into concrete changes; introduced AI agents into day-to-day development

• Delivered short-staffed: when the team shrank from 8 developers to 2, restructured scope, introduced AI-assisted development to hold the schedule and took on Go backend work alongside my own frontend scope

• Architecture and code: defined the architecture for every project in the portfolio — the structure the rest of the team built within — and wrote roughly 90% of the frontend code myself, from SSR applications with Next.js and Remix to cross-platform apps with Capacitor

• From zero to production: took a practice management platform — administration, inventory, integrated online shop, chat messenger — from an empty repository to production. Live in 7 markets with at least 7 more coming up, serving tens of thousands of users

• Delivery under pressure: built and shipped a replacement online shop for a Fortune 250 client in 4 days, restoring order intake while their global shops had been offline for several weeks

• Design system: built a cross-project design system used across 7 products, so new projects and features started from a shared, consistent base

• Cross-platform and real-time: built iOS and Android apps with Capacitor for a client live event with 1,000+ participants — web sockets and push notifications for real-time content, Stripe payments supporting PayPal, Apple Pay, Google Pay and cards

Key technologies: React, TypeScript, Next.js, Remix, GraphQL, ConnectRPC, Redux, Zustand, Go, Node.js, Turborepo, Nx, Capacitor, Ionic, WebSockets, Stripe, PostgreSQL, Playwright, Cypress, Vitest, Storybook, GitHub Actions, GitLab CI, Claude Code, Cursor, GitHub Copilot

• Lead architect for an enterprise loan digitisation programme, coordinating 12 engineers across five workstreams and serving as final technical authority on system design.
• Cut critical application response times by 68% (display 17.3s → 5.6s; modification 11.8s → 5.0s) through targeted caching, OData query optimisation and lazy-loading refactoring; further optimisation in progress.
• Own production error triage, prioritisation and resolution across a multi-application portfolio supporting live lending operations.
• Design and implement SAP Fiori applications on SAP UI5, TypeScript and RAP, owning delivery from architecture and code through rollout and production support.
• Established C4 architecture documentation and decision records for the full programme, enabling faster onboarding and consistent cross-workstream design governance.
• Co-managed S/4HANA release cycle alongside primary responsibilities, coordinating directly with SAP support to resolve critical system issues across the portfolio.

Self-directed exploration of agentic AI development methods, taken from idea to a working, publicly usable application

• Built an interactive planning tool for modelling retirement withdrawals and tax strategy using an agentic AI (vibe coding) development approach – demonstrating self-directed investigation of new AI-assisted development methods
• Delivered live, tax-aware spending projections and adjustable user inputs; shipped as a free, install-free browser application built in Python, with attention to usability for non-technical users

Project:

• Migration of existing VB6 applications to C# (Web API, web app)
• Report development and risk management systems (C#, API interfaces, databases)
• Document archive (API interfaces, databases)

Team size: 9 people

• Reports for Risk and Credit Management Development and maintenance of report structures to support risk and credit decisions, including data modeling, validation, and automated delivery for business departments.
• Migration and maintenance of a legacy system to the latest version of .NET for the asset management system Planning and execution of the modernization of an existing asset management system, including code refactoring, performance optimization, test automation, and sustainable maintenance after migration.
• Replacement of the COM-based archive connection with a REST API Redevelopment of the connection of the document archive (HYPARCHIV) to a REST API based on OpenAPI/Swagger, including archiving with index and stamp fields as well as PDF export into the customer portal.
• Redesign of payment receipt processing Replacement of an existing Oracle PL/SQL process with a new implementation in C# based on a business concept, including business alignment, data modeling, and test coverage.
• Design and implementation of tests, creation of deployment pipelines, and documentation
• Further development and implementation of change requests.
• Regular code reviews within the team as well as optimization of application scalability and stability

Technologies: C#, .NET 10, ASP.NET, Unit of Work, IoC, Three-Tier Architecture, Entity Framework Core, DB First, Web API, Swagger, OpenAPI, Python, Oracle, HYPARCHIV, Azure, PowerBI, DevOps, AKS (Azure Kubernetes Service), GIT, xUnit, NSubstitute, TypeScript, Vue.js, Pinia,

Methods: agile development using Scrum

• Developing a professional appointment planner for organizations with specific, detailed requirements
• Evaluating various existing software solutions
• Creating a list of technical requirements
• Implementing these requirements
• Technologies under consideration: WebDAV, CalDAV, Rust, Baikal, OAuth, Keycloak

• Technical consulting to meet regulatory MiCA requirements for a digital trading platform
• Design and development of backend components and APIs to comply with transparency and auditability requirements
• Optimization of core functions in order execution and market data delivery with a focus on performance and reliability under high load
• Conducting job interviews and structured onboarding of new developers
• Successful and timely implementation of the regulatory MiCA requirements, ensuring uninterrupted operations
• Reduction of user issues and common support requests by fixing complex backend problems
• Strengthening the development team through effective onboarding, mentoring, and knowledge sharing

• Development and further development of e-invoicing solutions, interfaces for invoice processing, and implementation of regulatory requirements

Technology & methods: XRechnung, ZUGFeRD, EN 16931, XML, API integration, backend development, cloud services, automation, compliance, AI-supported document analysis

• Several projects in a police context
• Model and document police procedures/projects with Archimate (as-is/to-be) in the context of P20 (BKA)
• Create software architectures with microservices
• POC development with Springboot/Docker/Kubernetes
• Project size: 10 people
• Enterprise architecture management with Togaf and Archimate
• Backend software development Springboot
• DevOps with Kubernetes
• Implemented using: Java 17/21, Springboot 3, P20 architecture, Togaf, Archimate

• Data-analysis, Preparation, gathering and coordination of business requirements for retrieval of monthly- and long term (CLV – relevant) cost- and revenue-components per contract for a customer–base–grouping project (HUB–Project) for B2C-Postpaid-Controlling
• Concept and Implementation of cost- and revenue-KPIs calculation and corresponding CLV–reports (Oracle, Perl, SVN, MS SQL Server, MS Power BI, Serviceware Performance Analytics)
• Operational support of the HUB-Project – various ad-hoc reports, deployments, job-scheduling etc. (Oracle, SVN, BICSuite–Scheduler, DWSODA etc.)
• Analysis, implementation, retrieval and reporting of various physical and financial KPIs for B2P-Prepaid Business on an existing data-mart (Oracle, Perl)