Michel Neumann

Senior Fullstack Engineer

Payment & Banking Systems · Healthcare IT

About Me

With 10+ years of experience, I solve engineering challenges for businesses that need reliable payment systems, banking integrations, and scalable infrastructure. My work spans financial services and healthcare IT, building systems that connect to banking networks, automate complex financial workflows, process high-volume transactions, and maintain regulatory compliance. My core stack covers TypeScript, JavaScript, Java, libraries such as React, Node.js, and Spring Boot on the application layer, and AWS, Docker, Terraform, and PostgreSQL on the infrastructure side.

Work Experience

Senior Software Engineer

Nelly Solutions GmbH

Jul 2025 — Present

Berlin, Germany

Drove initiative to replace a legacy PDF generation system for invoice processing with a React-based solution, reducing render time and file size while improving developer experience through code-first templating
Participated in infrastructure and deployment modernisation efforts across multiple engineering teams
- ›Migrated production services from shared EC2 to ECS containers, identifying candidates, testing deployments, and executing phased rollouts for zero-downtime transitions
- ›Prepared team-owned services for Continuous Deployment adoption, improving test coverage, enforcing pre-merge quality gates and briefing engineers on deployment processes
Contributed to migration of invoice processing between factoring providers with minimal service disruption
Built and enhanced internal tooling for factoring operations, streamlining invoice generation, partner bank reporting, and reconciliation workflows

[TypeScript][React][Node.js][AWS][Docker][PostgreSQL][Terraform][GitHub Actions][LaunchDarkly]

Senior Software Engineer

Klarna Bank AB

Jan 2022 — Jun 2025

Berlin, Germany

Built Java-based backend systems enabling Klarna's connectivity to banking networks (SEPA, SWIFT) with idempotent API design and concurrency-safe transaction handling, processing €1M+ daily while ensuring PSD2 and GDPR compliance
Tech-led automation of monthly fee processing using AWS Step Functions, reducing operational overhead by 12.5% for a serverless system serving hundreds of thousands of Klarna Card users across US and UK, generating ~20M SEK since launch
Developed customer-facing features for the Klarna App: card activation, credit card management, and native wallet integrations (Apple Pay, Google Pay) serving millions of users
- ›Led technical investigations supporting compliance requirements for US military service members
- ›Delivered system supporting the Klarna Card product proposition in GB markets
- ›Contributed to redesign of 'Card Home' and activation flows, reducing errands and increasing engagement
Built Klarna Card functionality for the internal customer service platform, supporting ~400 active agents daily with statements, forbearance, deferrals and transaction history tooling
Served as 'Readiness Lead' coordinating 20+ teams for load testing and compliance, resulting in zero incidents in the Card & Banking domain during Black Friday peak traffic

[Java][Spring Boot][AWS][React Native][PostgreSQL][Datadog][Jenkins]

Software Engineer

Spreewunder

Jul 2018 — Dec 2021

Berlin, Germany

Tech-led development of an on-premise video surveillance platform for retail, architecting backend systems to support 64-camera deployments with DASH/HLS streaming, plus client consultation and full-stack implementation in Python and Angular
- ›Delivered a system capable of displaying up to 64 camera feeds in a browser in real-time, running 24/7 in an intranet environment with motion-triggered and AI-powered segment capture
- ›Designed and implemented peer-to-peer infrastructure for the 'Secuvid' video conferencing SDK using WebRTC, with end-to-end encryption, licensed to a German healthcare patient management provider
Created API interfaces for SDK components and enabled package-based distribution
- ›Built a real-time cardiovascular data analysis app integrating Bluetooth 12-lead ECGs, training AI models for heart data classification and developing a web-based interface for clinical use

[Python][Angular][JavaScript][WebRTC][REST APIs][Docker]

Software Engineer

Fraunhofer FOKUS

May 2016 — Jun 2018

Berlin, Germany

Contributed to the 'Cloudless' framework, implementing a WebRTC-based peer-to-peer data synchronization layer for backend-less, end-to-end encrypted applications
Developed backend solutions and IoT prototypes using Node.js, supporting research projects in distributed systems and connected devices

[Node.js][JavaScript][WebRTC][IoT]

Web Development Intern

Wazoku

Oct 2014 — Mar 2015

London, United Kingdom

Contributed to the 'Idea Spotlight' innovation management platform using AngularJS and Python
Rebuilt and relaunched the company website using WordPress and PHP, collaborating with design and marketing teams

[AngularJS][Python][WordPress][PHP]

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Education

M.Sc. International Media & Computing

HTW Berlin

2012 — 2018 · Berlin, Germany

Master thesis: 'Application of artificial neural networks in web browsers using ECG data' (grade 1.5)

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Certifications

AWS Solutions Architect Associate

SAA-C03

AWS Certification · November 2023

Acquired the AWS Solutions Architect SAA-C03 certification to enhance my skill set and advance my career in cloud computing.

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Languages

GermanNative
EnglishFluent