Rudi Zeilhofer, Developer in Munich, Bavaria, Germany
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Rudi Zeilhofer

Verified Expert  in Engineering

Software Developer

Munich, Bavaria, Germany
Toptal Member Since
October 27, 2021

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.


Toptal Client
Ruby on Rails (RoR), PostgreSQL, JavaScript, Agile Software Development...
Toptal Client
Ruby, Ruby on Rails (RoR), MySQL, Vue, JavaScript, Algolia, RabbitMQ...
ETL, Python 3, Python, NumPy, Pandas, Tableau Server, Tableau...




Preferred Environment

Visual Studio Code (VS Code), Slack, Ruby on Rails (RoR), Office 365, Miro, Atlassian Suite, Git, Docker, Amazon Web Services (AWS), Jenkins

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

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

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

Senior Data Engineer

2019 - 2021
  • 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

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

Senior Full-stack Software Developer

2015 - 2017
  • 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

Senior Full-stack Software Developer

2007 - 2009
  • 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

Senior Full-stack Software Developer

1999 - 2006
  • 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

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.

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.

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.


Ruby, CSS, HTML, SQL, HTML5, JavaScript, PHP, Perl, GraphQL, Java, Python 3, Python, TypeScript


Ruby on Rails (RoR), Ruby on Rails 3, Ruby on Rails 4, Ruby on Rails 5, AWS HA, Hadoop, Swagger


REST APIs, Vuex, Web API, Sidekiq, Vue, Vue 2, React, jQuery, NumPy, Pandas, Salesforce API, Apache Lucene, Node.js


Atlassian Suite, RSpec, Tableau, Microsoft Excel, Git, Jenkins, Tableau Desktop Pro, React Apollo, RabbitMQ, Slack, Microsoft Teams, Salesforce Sales Cloud, Microsoft Dynamics, GitLab CI/CD, Docker Compose, Google Analytics, CircleCI, Code Climate, SimpleCov, RuboCop, Optimizely, Amazon EKS


Scrum, Agile, Agile Software Development, Test-driven Deployment, REST, Test-driven Development (TDD), Management, Unit Testing, Microservices, ETL, Objectives & Key Results (OKRs), Key Performance Metrics, Business Intelligence (BI), Continuous Deployment, Continuous Integration (CI), Design Thinking, Plain Old Ruby Object (PORO), Refactoring


Amazon EC2, MacOS, Visual Studio Code (VS Code), Amazon Web Services (AWS), Algolia, Docker, Apache Kafka, Salesforce


NoSQL, JSON, PostgreSQL, Redis, MongoDB, MySQL, Cassandra, Elasticsearch


Software Development, Continuous Learning, Autoscaling, Cloud, Elastic Load Balancers, Product Development, Ruby on Rails 7, Legacy Code, Team Leadership, Team Mentoring, Technical Leadership, Back-end, Performance, Miro, Software Architecture, Agile Coaching, Tableau Server, Leadership, Product Owner, Moderation, Business Model Canvas, Value Proposition Design, Apache Flume, Cross-functional Collaboration, DataFrames, Reporting, Dashboard Design, APIs, Apollo, Training, Scalability, Office 365, Computational Linguistics, Algorithms, Coaching, Scrum Master, Product-led Growth (PLG), Go-to-market Strategy, Facilitation, Apollo Server, Sitecore, Platforms, Ruby Gems, Marketing Platforms, Full-stack, Architecture, Knowledge Management, Amazon RDS

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


Apollo Graph Developer – Associate

Apollo GraphQL

JULY 2021 - JULY 2023

AWS Certified Cloud Practitioner



Product-Led Growth Foundation

PLG Institute Wes Bush


Certified Coach for Collegial Leadership

Bernd Oestereich – Werkstatt für Kollegiale Führung


OKR Masterclass

Felipe Castro


Agile Team Facilitation

it-agile GmbH

MARCH 2017 - MARCH 2023

Certified Scrum Product Owner

Scrum Alliance


Value Proposition Design