Rudi is available for hire
Hire RudiRudi Zeilhofer
Verified Expert in Engineering
Software Developer
Munich, Bavaria, Germany
Toptal member since October 27, 2021
Bio
Rudi is a multidisciplinary Agile servant leader known for successfully guiding amazing teams, fast-growing companies, and their awesome products to the next level. Rudi is a Swiss Army Knife with 20+ years of cross-functional experience in Agile software development, combined with state-of-the-art know-how, technological curiosity, and a pragmatic approach to using best practices.
Portfolio
Zenkita
Ruby, Ruby on Rails 8, React, TypeScript 5, PostgreSQL, Pgvector...
Owens Corning | F500 | Digital Center of Excellence
Ruby on Rails (RoR), Microservices, JavaScript, SQL, React, AWS ELB...
Owens Corning | F500 | Customer Center of Excellence
Ruby on Rails (RoR), Microservices, JavaScript, SQL, React, Danger, Codecov...
Experience
- Software Development - 20 years
- Ruby on Rails (RoR) - 12 years
- Ruby - 12 years
- PostgreSQL - 10 years
- Software Architecture - 7 years
- Amazon Web Services (AWS) - 7 years
- React - 4 years
- Agile Coaching - 3 years
Preferred Environment
Visual Studio Code (VS Code), Slack, Ruby on Rails (RoR), Office 365, Miro, Atlassian Suite, Docker, Amazon Web Services (AWS), GitHub Actions, Figma
The most amazing...
...real-time event pipeline I've established analyzes customer behavior and quantifies satisfaction, scaling it to 1,000,000 DAU and 1,000+ events per sec on AWS.
Work Experience
Lead Software Developer
2025 - 2026
Zenkita
- Developed a multi-LLM extraction system that automatically processes German receipts and invoices with confidence scoring, eliminating manual data entry and reducing document processing time from minutes to seconds.
- Built a vector search pipeline using pgvector and OpenAI embeddings, enabling natural language queries across financial documents instead of exact keyword matching—transforming how users discover information.
- Architected a SaaS platform on Ruby 4.0/Rails 8.1 with React 19 as a modular monolith, enabling independent domain teams while maintaining single-deployment simplicity.
- Implemented Argon2 hashing, JWT auth, and multi-tier rate limiting with breach detection, protecting sensitive financial data while meeting German data protection requirements.
- Integrated n8n for orchestrating bank imports and reconciliation workflows, reducing manual intervention and enabling the operations team to scale from dozens to hundreds of customers.
- Established 100% test coverage, automated security scanning, and comprehensive API documentation, enabling rapid iteration while maintaining stability for financial software.
Technologies: Ruby, Ruby on Rails 8, React, TypeScript 5, PostgreSQL, Pgvector, Large Language Models (LLMs), Ollama, Mistral AI, OpenAI API, Embeddings from Language Models (ELMo), Semantic Search, n8n, OpenAPI, Orval, TanStack Router, TanStack Query, TanStack Form, Tailwind CSS, Shadcn UI, JSON Web Tokens (JWT), Domain-driven Design (DDD), Modular Design, Solid Queue, RSpec, Vite, Vitest, Zustand, Playwright, V8, SimpleCov, Docker, Docker Compose, AWS ECS Fargate, AWS CloudFormation, Figma, Human-in-the-loop (HITL), Human-centered AI, Claude Code, Codex, Visual Studio Code (VS Code), Cursor AI, Kiro, Spec Driven Design (SDD)
Engineering Manager | Senior Full-stack Developer | Fortune 500 Industrial Company
2024 - 2025
Owens Corning | F500 | Digital Center of Excellence
- Led a multi-disciplinary team, improving coding standards, CI/CD, DevOps, and security, while optimizing AWS costs. Servant leader balancing hands-on work with strategy, team growth, and customer value.
- Fostered open communication, cross-team collaboration, and a culture of continuous improvement.
- Improved coding guidelines, automated code reviews, and made unit test coverage visible, boosting quality and maintainability.
- Led DevOps and application security initiatives: created cross-team CI/CD strategy, migrated legacy deployments to Docker-based applications, and developed roadmaps to strengthen application, tech stack, and infrastructure security.
- Categorized technical debt, prioritized projects, and created roadmaps for upgrading applications and technical stacks.
- Analyzed AWS cloud expenses and helped form a strategy to reduce costs by over 60%.
- Established clear code ownership using GitHub CODEOWNERS guidelines, shifting the culture from “works-for-me” to accountability and shared responsibility.
- Combined expertise in software development, DevOps, application security, and engineering leadership to deliver customer value, foster team growth, and enable high-performing systems.
- Led with vision and servant leadership—empowering teams to grow, innovate, and deliver. Aligned technical excellence with business goals through analytical and strategic thinking, ensuring valuable outcomes, transparency, and team happiness.
Technologies: Ruby on Rails (RoR), Microservices, JavaScript, SQL, React, AWS ELB, AWS CodeBuild, AWS CodePipeline, AWS CloudFormation, Amazon CloudWatch, Danger, Codecov, CircleCI, GitHub Actions, ESLint, RuboCop, RSpec, Jest, OpenAPI, Packwerk, Auto-scaling Cloud Infrastructure, Amazon S3 (AWS S3), Slack API, Team Leadership, Servant Leadership, Engineering Management, SonarQube, Docker, Amazon Elastic Container Registry (ECR), Brakeman, Legacy Code, IT Security, Ruby Gems, Node.js, Clean Code, Code Review, Sentry, AWS ECS Fargate, Elastic Load Balancers, API Integration
Senior Full-stack Developer | Fortune 500 Industrial Company
2023 - 2024
Owens Corning | F500 | Customer Center of Excellence
- Improved coding standards, CI/CD, DevOps, and security, while improving development ways of working to the next level. Servant lateral leader balancing hands-on work with strategy, team growth, and customer value.
- Fostered open communication, cross-team collaboration, and a culture of continuous improvement.
- Improved coding guidelines, automated code reviews, and made unit test coverage visible, boosting quality and maintainability.
- Led DevOps and application security initiatives: created cross-team CI/CD strategy, migrated legacy deployments to Docker-based applications, and developed roadmaps to strengthen application, tech stack, and infrastructure security.
- Categorized technical debt, prioritized projects, and created roadmaps for upgrading applications and technical stacks.
- Established clear code ownership using GitHub CODEOWNERS guidelines, shifting the culture from “works-for-me” to accountability and shared responsibility.
- Combined expertise in software development, DevOps, application security, and engineering leadership to deliver customer value, foster team growth, and enable high-performing systems.
- Led with vision and servant leadership—empowering teams to grow, innovate, and deliver. Aligned technical excellence with business goals through analytical and strategic thinking, ensuring valuable outcomes, transparency, and team happiness.
Technologies: Ruby on Rails (RoR), Microservices, JavaScript, SQL, React, Danger, Codecov, CircleCI, GitHub Actions, RuboCop, RSpec, Jest, OpenAPI, Packwerk, Slack API, Servant Leadership, Development, SonarQube, Sentry, Docker, Brakeman, Legacy Code, IT Security, Ruby Gems, Node.js, Clean Code, Code Review, AWS ECS Fargate, AWS CodeBuild, AWS CodePipeline, Auto-scaling Cloud Infrastructure, TypeScript, API Integration
Senior Back-end RoR Developer
2022 - 2023
Toptal Client
- Established a green-field RoR project with RoR best practices regarding automatic lining, RSpec testing, code coverage, and a GitHub pipeline featuring Code Climate and CircleCI.
- Migrated complex API endpoints from Node.js/TypeScript services, ensuring they were well-structured, easy to maintain, and fully documented. As a result, a robust REST API was established.
- Built up fast know-how about the financial sector and the existing features to migrate and implement new ideas from scratch in close cooperation with product managers.
- Defined and documented API endpoints with Swagger (OpenAPI) for easier collaboration between front-end and back-end teams, focusing on backward compatibility.
- Improved collaboration and working methods by driving feedback channels (daily standup and retros), know-how transfer, mentoring engineers, teaching Ruby skills, and visualizing features.
Technologies: Ruby on Rails (RoR), PostgreSQL, JavaScript, Agile Software Development, TypeScript, Node.js, CircleCI, Code Climate, SimpleCov, RSpec, RuboCop, Full-stack, Swagger, REST APIs, Refactoring, Architecture, Knowledge Management, Optimizely, Back-end, Microservices, Sidekiq, Scalability, Performance, API Integration
Senior Full-stack Developer
2022 - 2022
Toptal Client
- Developed an eCommerce shopping list feature. Built the back-end RESTful API in Ruby on Rails and front end in Vue.js and Vuex.
- Dockerized the app and set up GitLab CI/CD, including full test coverage. Integrated the Algolia search engine via Algolia API and Ruby client.
- Designed and implemented a system for a synchronization service between various APIs, such as MS Dynamics 365, Moosend API, and Sitecore CRM. Decoupled data extraction and data loading via RabbitMQ.
- Collaborated remotely using Jira, Miro, and Slack. Organized and streamlined projects, epics, and stories in an outcome-oriented and user-centered fashion.
- Created high-level visualizations with Miro to enable effective discussions, speed-up decision-making, and create a high level of alignment.
- Adapted quickly to a huge legacy codebase with 100+ classes and database tables. Improved overall test coverage and code stability.
Technologies: Ruby, Ruby on Rails (RoR), MySQL, Vue, JavaScript, Algolia, RabbitMQ, Legacy Code, Ruby Gems, Docker, GitLab CI/CD, Docker Compose, Continuous Integration (CI), REST, REST APIs, Elasticsearch, Vuex, Unit Testing, Team Mentoring, Technical Leadership, HTML5, JSON, Back-end, Microservices, API Integration
Senior Data Engineer
2019 - 2021
Xempus
- Planned and implemented data warehouse architecture, data pipelines, and ETL stages. Accelerated the data-driven organization by enabling data accessibility via Salesforce and Tableau for all employees.
- Implemented ETL in Python, NumPy, and Pandas DataFrame. Heavy usage of Salesforce API for extraction and loading of data.
- Changed data into real value by implementing (Python) an algorithm to quantify user satisfaction and easily accessible metrics and user cohorts.
- Concepted and implemented the product-led growth framework as a customer-centered growth strategy in cooperation with sales, product, marketing, customer success, and engineering.
Technologies: ETL, Python 3, Python, NumPy, Pandas, Tableau Server, Tableau, Tableau Desktop Pro, Salesforce Sales Cloud, Salesforce, Product-led Growth (PLG), Salesforce API, Management, SQL, APIs, REST APIs, Unit Testing, Team Mentoring, Technical Leadership, HTML5, JSON, Scalability, Performance, Amazon EKS, API Integration
Engineering Manager
2018 - 2019
Xempus AG
- Simplified the way-of-working of two customer-faced teams by strengthening team collaboration, implementing efficient customer service tool stack, streamlining product portfolio, and excelled team efficiency by automation internally and client-side.
- Achieved an 80% cost reduction for onboarding new insurance partners and their data by a massive decrease of complexity, lean processes, and time-saving client-side testing tools.
- Enhanced the data exchange API from scripted Ruby to a CI/CD Java service, including automated error reporting and Jira ticketing in close cooperation with external insurance partners.
Technologies: Ruby, Ruby on Rails (RoR), Java, PostgreSQL, Apache Kafka, Management, SQL, Product Development, Ruby on Rails 5, Google Analytics, Team Leadership, Team Mentoring, Technical Leadership, HTML5, JSON, Performance, Engineering Management
Senior Full-stack Software Developer
2015 - 2017
Xempus
- Designed and implemented a B2B SaaS web application for the management of company pension schemes on Ruby on Rails, JavaScript, jQuery, and PostgreSQL stack.
- Scaled the Agile development process up to 10+ employees. Improved Agile software development and team excellence by using CI/CD, QA and defect management, versioning, and Scrum.
- Released the first production version on time and in scope with several integrated insurance partners.
- Scaled the Scrum process to several distributed teams and adaptation of the software tool stack.
Technologies: Ruby, Ruby on Rails (RoR), PostgreSQL, React, jQuery, JavaScript, Continuous Deployment, Continuous Integration (CI), CSS, HTML, RSpec, Test-driven Development (TDD), Management, SQL, Product Development, REST APIs, Plain Old Ruby Object (PORO), Ruby on Rails 4, Unit Testing, Team Leadership, Team Mentoring, Technical Leadership, HTML5, JSON, Back-end, Performance
Senior Full-stack Software Developer
2009 - 2014
Scoreloop AG
- Concepted, architected, and implemented an AWS Cloud-hosted API back end in Ruby on Rails and Ember.js.
- Scaled the real-time leaderboard API for more than 1,000 events per second.
- Established a real-time event pipeline, including big-data storage, real-time analytics, and Tableau BI, for analyzing customer behavior and on-demand reporting.
Technologies: Ruby on Rails (RoR), Apache Flume, Amazon EC2, Amazon Web Services (AWS), PostgreSQL, Ruby, Redis, MongoDB, Hadoop, Cassandra, CSS, HTML, RSpec, Test-driven Development (TDD), SQL, APIs, Product Development, REST APIs, NoSQL, Ruby on Rails 3, Unit Testing, Team Leadership, Team Mentoring, Technical Leadership, Scalability, Performance, AWS ELB, Auto-scaling Cloud Infrastructure, Amazon S3 (AWS S3), Engineering Management
Senior Full-stack Software Developer
2007 - 2009
Trupoli
- Concepted, architected, and implemented a B2C web application in Ruby on Rails.
- Scaled the development team and its Agile processes to 10+ employees, including technical and disciplinary management.
- Co-founded this e-government and social media startup with a vision of more transparent politics—True Politics. The startup had 35 employees.
Technologies: Ruby on Rails (RoR), Ruby, MySQL, CSS, HTML, RSpec, Management, SQL, Product Development, Unit Testing, Team Leadership, Team Mentoring, Technical Leadership, Engineering Management
Senior Full-stack Software Developer
1999 - 2006
Pangora
- Innovated and built an eCommerce search engine with variable layout and theming in Perl and later in PHP, including in-house infrastructure operations and on-premise hosting.
- Scaled the software development department to 30+ employees, including technical and disciplinary management and outsourcing (10 MA in Armenia).
- Gained my first IRL experience with an Agile development process and extreme programming (XP).
Technologies: PHP, Perl, MySQL, CSS, HTML, Management, SQL, Product Development, Apache Lucene, Unit Testing, Team Leadership, Team Mentoring, Technical Leadership, Scalability, Performance, Engineering Management
Experience
Xempus Manager
A Ruby-on-Rails-based SaaS web platform for managing pension funds. Its front-end technology changed from React to Vue.js over time. I acted as a lead full-stack developer and team lead. This was a green-field project with a hard deadline, and I delivered the first release on time and in scope. Modern development stack with CI/CD, test-driven, Agile, Scrum, and T-shaped team.
Quantify Customer Experience in Salesforce
The project goal was to get detailed insights into customer behavior, loyalty, and conversion rates transforming existing application data into Salesforce accessible information and metrics. Additionally, I was in charge of finding a suitable modern growth strategy enabling the sales, marketing, product, and customer success departments to optimize customer satisfaction and improve overall SaaS subscription-based revenue.
I introduced product-led growth as a growth framework and designed various activation, adoption, conversion, loyalty metrics, and a detailed customer journey from newbie to enthusiast level.
On the engineering side, I was in charge of designing and implementing the data architecture and transformation stages, extracting data from various application database sources, merging independent user bases, transforming raw data into valuable insights, and storing the results into a data warehouse. Data and metrics became accessible from Tableau (BI) and Salesforce.
Tech stack included ETL with Python3 with NumPy and Pandas DataFrame, Tableau Prep, Tableau Server, and Salesforce API.
Besides that, I supported colleagues in their learning curve to become more data-driven and confident with BI tools and Salesforce.
I introduced product-led growth as a growth framework and designed various activation, adoption, conversion, loyalty metrics, and a detailed customer journey from newbie to enthusiast level.
On the engineering side, I was in charge of designing and implementing the data architecture and transformation stages, extracting data from various application database sources, merging independent user bases, transforming raw data into valuable insights, and storing the results into a data warehouse. Data and metrics became accessible from Tableau (BI) and Salesforce.
Tech stack included ETL with Python3 with NumPy and Pandas DataFrame, Tableau Prep, Tableau Server, and Salesforce API.
Besides that, I supported colleagues in their learning curve to become more data-driven and confident with BI tools and Salesforce.
Scaling Mobile Gaming Leaderboards with Ruby on Rails, MongoDB, and Redis
A Ruby on Rails-based back-end API for the Scoreloop cross-platform mobile gaming SDK. The SDK contained social features for mobile gaming like challenges, regional and global leaderboards, gaming currencies, and badges.
With popular games implementing the Scoreloop SDK, we needed to scale the ever-growing leaderboards for popular games like Cut the Rope or Plants vs. Zombies. Starting with PostgreSQL, we switched to AWS-EC2 instances with Redis in-memory leaderboards. Back-end API implemented in RoR and leaderboard Redis services could deal with 1,000+ events per second and could be easily scaled horizontally during peak times.
With popular games implementing the Scoreloop SDK, we needed to scale the ever-growing leaderboards for popular games like Cut the Rope or Plants vs. Zombies. Starting with PostgreSQL, we switched to AWS-EC2 instances with Redis in-memory leaderboards. Back-end API implemented in RoR and leaderboard Redis services could deal with 1,000+ events per second and could be easily scaled horizontally during peak times.
Data Synchronization Between CRM and Marketing Platform
A data synchronization service between three data sources—Microsoft Dynamics, Sitecore CMS, and a proprietary RESTful service with an email-marketing platform as the destination.
My tasks included decoupling source and destination clients with RabbitMQ, idempotency, intelligent error handling, recovery, and notification. It was implemented as a detailed proof-of-concept with Ruby on Rails.
My tasks included decoupling source and destination clients with RabbitMQ, idempotency, intelligent error handling, recovery, and notification. It was implemented as a detailed proof-of-concept with Ruby on Rails.
Education
2019 - 2020
Master's Degree in Agile Coaching
Judith Andresen Beratung (JAB) - Hamburg, Germany
1994 - 1999
Coursework in Computer Science
Ludwig-Maximilians-Universität München - München, Germany
Certifications
NOVEMBER 2021 - PRESENT
Apollo Graph Developer – Associate
Apollo GraphQL
JULY 2021 - JULY 2023
AWS Certified Cloud Practitioner
AWS
FEBRUARY 2021 - PRESENT
Product-Led Growth Foundation
PLG Institute Wes Bush
DECEMBER 2018 - PRESENT
Certified Coach for Collegial Leadership
Bernd Oestereich – Werkstatt für Kollegiale Führung
OCTOBER 2018 - PRESENT
OKR Masterclass
Felipe Castro
MARCH 2018 - PRESENT
Agile Team Facilitation
it-agile GmbH
MARCH 2017 - MARCH 2023
Certified Scrum Product Owner
Scrum Alliance
MARCH 2016 - PRESENT
Value Proposition Design
Strategyzer
Skills
Libraries/APIs
REST APIs, Vuex, Web API, Sidekiq, React, Vue, Vue 2, Node.js, OpenAPI, jQuery, NumPy, Pandas, Salesforce API, Apache Lucene, Slack API, OpenAI API, Playwright
Tools
Atlassian Suite, RSpec, CircleCI, SimpleCov, RuboCop, AWS CloudFormation, Amazon Elastic Container Registry (ECR), Tableau, Microsoft Excel, Miro, Git, Jenkins, Tableau Desktop Pro, React Apollo, RabbitMQ, GitLab CI/CD, Docker Compose, AWS ELB, AWS CodeBuild, Codecov, Sentry, Slack, Microsoft Teams, Salesforce Sales Cloud, Microsoft Dynamics, Google Analytics, Code Climate, Optimizely, Amazon EKS, Amazon CloudWatch, SonarQube, Figma, n8n, TanStack Router, Shadcn UI, Vitest, V8, Claude Code, Codex, Kiro
Languages
Ruby, CSS, HTML, SQL, HTML5, JavaScript, PHP, Perl, GraphQL, TypeScript, Java, Python 3, Python, TypeScript 5
Frameworks
Ruby on Rails (RoR), Ruby on Rails 3, Ruby on Rails 4, Ruby on Rails 5, Ruby on Rails 7, AWS HA, Swagger, Jest, Hadoop, Tailwind CSS, JSON Web Tokens (JWT)
Paradigms
Scrum, Agile, Agile Software Development, Test-driven Deployment, REST, Test-driven Development (TDD), Management, Unit Testing, Refactoring, Microservices, Clean Code, ETL, Objectives & Key Results (OKRs), Key Performance Metrics, Business Intelligence (BI), Continuous Deployment, Continuous Integration (CI), Design Thinking, Plain Old Ruby Object (PORO), Modular Design
Platforms
Amazon EC2, MacOS, Visual Studio Code (VS Code), Amazon Web Services (AWS), Algolia, Docker, Apache Kafka, Salesforce, Ollama
Storage
NoSQL, JSON, Auto-scaling Cloud Infrastructure, Amazon S3 (AWS S3), PostgreSQL, Redis, MongoDB, MySQL, Cassandra, Elasticsearch
Other
Software Development, Continuous Learning, Autoscaling, Cloud, Cross-functional Collaboration, Elastic Load Balancers, Product Development, Legacy Code, Ruby Gems, Team Leadership, Team Mentoring, Technical Leadership, Full-stack, Architecture, Back-end, Performance, AWS CodePipeline, AWS ECS Fargate, Danger, Packwerk, Engineering Management, Brakeman, Code Review, Development, API Integration, Software Architecture, Agile Coaching, Tableau Server, Leadership, Product Owner, Moderation, Business Model Canvas, Value Proposition Design, Apache Flume, DataFrames, Reporting, Dashboard Design, APIs, Apollo, Training, Scalability, GitHub Actions, IT Security, Office 365, Computational Linguistics, Algorithms, Coaching, Scrum Master, Product-led Growth (PLG), Go-to-market (GTM) Strategies, Facilitation, Apollo Server, Sitecore, Platforms, Marketing Platforms, Knowledge Management, Amazon RDS, ESLint, Servant Leadership, Ruby on Rails 8, Pgvector, Large Language Models (LLMs), Mistral AI, Embeddings from Language Models (ELMo), Semantic Search, Orval, TanStack Query, TanStack Form, Domain-driven Design (DDD), Solid Queue, Vite, Zustand, Human-in-the-loop (HITL), Human-centered AI, Cursor AI, Spec Driven Design (SDD)
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