Lead Software Engineer (m/f/d) - Java, IDP & AI Platform

retarus GmbH; München; Hybrid; EUR 120,000 - 170,000; Full time

Benefits offered by this job

Mobile working

Flexible working time

Collaborative culture

Flat hierarchies

Development opportunities

International collaboration

Modern offices

Health insurance & transport & lunch

Job summary

Retarus GmbH seeks a Lead Software Engineer (m/f/d) to drive the IDP/AI Platform with hands-on Java/Spring development and architectural leadership. You will shape the platform's evolution toward AI/LLM-based solutions and coordinate with external partners to build long-term ownership.

You will lead design reviews, guide engineers, and ensure scalable, observable services while maintaining production-grade quality. German and English fluency are essential for collaboration across teams.

Qualifications

• Completed university degree in Computer Science, Software Engineering or related field with at least 7 years of software experience.
• Strong Java and Spring Boot expertise with backend/service design experience.
• Experience with distributed systems, REST APIs, messaging, CI/CD, and observability.
• Ability to lead technically, review code/design, and collaborate with external partners.
• Excellent German and English communication.

Responsibilities

• Take on technical lead for our IDP platform, combining hands-on coding and architectural responsibility.
• Drive modernization of the Java/Spring-based platform with clean interfaces and testable components.
• Define target architecture with Product/Engineering/Management for AI/LLM evolution.
• Evaluate options like migration, modular extensions, cloud APIs, or on-prem deployment.
• Review designs, code, and architecture; ensure scalable, observable, and operable components.
• Contribute hands-on to backend and platform components using Java/Spring Boot and related tech.

Skills

Java

Spring Boot

Backend design

Python AI

Distributed systems

REST APIs

CI/CD

Observability

German & English

AI/ML/LLM tech

Technical leadership

Education

Bachelor's or Master's in CS/Software Engineering

Job description

Become Lead Software Engineer (m/f/d) - Java, IDP & AI Platform at Retarus.

Retarus is a worldwide provider of cloud-based messaging solutions at enterprise scale. We serve over 40% of the companies listed on the S&P Global 100, e.g. Adidas, Bayer, SAP, BNP Paribas, Goldman Sachs, T-Systems, Swarovski and UPS, as well as governmental agencies and major players in markets across the world. Privately owned and founder-managed for over thirty years, Retarus is customer-oriented, stable, a fair employer, and a strategic business partner with a long-term vision. With some 500 employees in 19 offices on four continents, Retarus operates locally and thinks globally: our teams are organized across borders and are highly integrated. This makes Retarus a multicultural, multilingual, and engaging workplace. We are committed to creating a diverse and dynamic environment for our employees, with generous compensation, time off, and a global, collaborative workplace.

Your role

As a Lead Software Engineer, you will play a key technical role in the further development of our Intelligent Document Processing platform. You will drive the technological evolution of the existing system, ensuring stability, scalability, and maintainability, while also playing a major role in its potential transformation towards a modern AI/LLM-based architecture. Working hands‑on within the engineering team, you will provide technical leadership, drive architectural decisions, and support collaboration with external development partners – with the goal of building long‑term technological ownership and expertise within the company.

What we offer

• Mobile working and flexible working time
• Collaborative, diverse company culture and superior team spirit
• Flat hierarchies and great feedback culture
• Development opportunities & career perspective
• International business & cross‑site collaboration
• Modern, dog‑friendly offices with nice amenities
• Company‑paid health insurance, public transportation, lunch vouchers and further benefits

What you'll do

• Take on the technical lead role for our Intelligent Document Processing platform, combining hands‑on software engineering, architectural responsibility, and technical team leadership
• Drive the technological evolution of our existing Java/Spring‑based platform, including the stabilization and modernization of existing services while ensuring clean interfaces, maintainability, testability, and production‑ready quality
• Define the target architecture together with Product, Engineering, and Management, including the potential evolution from traditional ML/OCR‑based approaches towards modern AI/LLM‑based IDP architectures
• Evaluate technical options such as brownfield migration, parallel partial redevelopment, modular service extensions, cloud API integration, or on‑premises GPU deployment, and derive pragmatic implementation steps
• Take responsibility for design reviews, code reviews, and architectural decisions while ensuring scalable, secure, observable, and operationally manageable components
• Contribute hands‑on to key backend and platform components, particularly using Java/Spring Boot, service‑oriented architectures, messaging, APIs, validation, OCR/document processing, Python‑based AI/inference services, monitoring, observability, and integration logic
• Integrate and modularize AI/ML/LLM functionalities and reduce system complexity, for example through clearly defined model adapters, prompt and configuration management, OCR/extraction services, inference services, and flexible cloud/on‑premises deployment models
• Technically manage external development partners, including reviewing concepts and implementations, ensuring transparent technical decision‑making, and building internal technical ownership through documentation, reviews, and targeted knowledge transfer
• Analyze and optimize the IDP pipeline in terms of latency, throughput, scalability, fault tolerance, and observability to ensure a production‑ready platform
• Coach engineers within the team, establish engineering best practices, and strengthen ownership, quality awareness, and a pragmatic, solution‑oriented development culture
• Contribute to a sustainable technical roadmap that balances short‑term delivery requirements with the long‑term platform strategy

What you'll need

• A completed university degree (Bachelor’s or Master’s) in Computer Science, Software Engineering, or a comparable field, combined with at least 7 years of professional experience in Software Engineering or a comparable technical role
• Strong expertise in Java, Spring Boot, and the design of production‑ready backend and platform services, combined with sufficient technical breadth to evaluate Python‑based AI/inference components, model integrations, and internal IDP/AI libraries
• Solid experience with distributed systems, service‑oriented architectures, REST APIs, messaging/eventing, CI/CD, observability, and the operation of business‑critical applications
• Proven experience in evolving existing systems, including refactoring, modularization, reducing technical complexity, and developing pragmatic migration strategies while balancing long‑term architectural quality with short‑term delivery
• Strong technical understanding of modern AI/ML/LLM technologies, with the ability to assess approaches such as traditional ML models, generative LLMs, cloud AI APIs, and on‑premises inference based on quality, latency, cost, scalability, and operational requirements
• Strong technical leadership skills through mentoring, code and design reviews, and collaboration with external development partners, ideally including technical coordination, knowledge transfer, or the establishment of internal ownership
• Excellent communication and collaboration skills across team boundaries, a strong sense of ownership, a pragmatic hands‑on mindset, and very good German and English skills
• Ideally, experience with document processing, OCR, Intelligent Document Processing, ML/LLM‑based data extraction, EDI/B2B integration processes, or comparable data- and process‑driven platforms

What you can expect

At Retarus, you will work on impactful and dynamic projects, with real opportunities to make a difference. Our customers are leaders across diverse industries, with constantly evolving needs and high expectations. You’ll be working with cutting‑edge technology and great creative leeway to meet customers’ needs – and the projects you work on will be deployed globally. Working at Retarus, you will collaborate closely with convivial, culturally diverse teammates. You will grow professionally in a dynamic and exciting workplace and design impactful solutions in real time with top companies.

Very important
Come as you are. Retarus is committed to equal employment opportunity regardless of race, color, ancestry, religion, sex, national origin, sexual orientation, age, citizenship, marital status, disability, gender identity, or veteran status.

We’relookingforward to getting to know you!