Legacy Rails to React ecosystem transformation

A leading German social networking platform faced critical challenges with their monolithic Ruby on Rails application, which had grown historically and become difficult to maintain and scale efficiently. The company needed to align their technical architecture with their internal team structure, where each page was managed by a dedicated team. The profile page, being the heart of the network, required a complete transformation to a modern React ecosystem that could accommodate modular integrations from other teams.

Challenges

Initial situation, pain points, and setup:

• Legacy monolithic Ruby on Rails application with historical technical debt and maintenance challenges

• Need to align technical architecture with internal team structure where each page is managed by a dedicated team

• Profile page as the core of the social network requiring transformation to modern React architecture

• Requirement for a modular ecosystem allowing other teams to integrate their widgets (CV features, etc.) into the profile page

• Need to maintain consistency across UI, functionality, and version updates across multiple integrated modules

• Challenge of serving 22M+ monthly active users during the transformation process without service disruption

Objectives

Establish and lead a React transformation that enables:

• Complete migration from legacy Rails monolith to modern React architecture for the profile page

• Creation of a modular ecosystem allowing other teams to register and integrate their modules

• Development of internal SDK and NPM registry for standardized module development

• Hybrid rollout strategy maintaining legacy pages while gradually transitioning to React ecosystem

• Knowledge transfer and guidance for other teams on module development according to established guidelines

Expected outcomes:

• Modern, maintainable React architecture replacing legacy Rails code

• Modular ecosystem enabling efficient team collaboration and feature development

• Successful hybrid migration with zero service disruption for 22M+ users

• Established development standards and tools for future platform growth

Approach

• Started as React expert freelancer, then extended to backend engineer role to ensure full-stack transformation

• Designed and implemented a modular React ecosystem with sandboxed module architecture

• Created internal SDK for profile page module development with comprehensive guidelines and documentation

• Established internal NPM registry for node packages and demo applications as development environments

• Implemented hybrid migration strategy: keeping legacy Rails pages while rolling out React pages incrementally

• Provided training and guidance to other teams on module development standards and best practices

Obstacles

• Complex coordination across multiple internal teams with different development methodologies and priorities

• Need to maintain service quality for 22M+ monthly active users during the transformation process

• Challenge of creating a modular architecture that maintains consistency across diverse team implementations

• Requirement to balance development velocity with architectural quality and system stability

• Risk of technical debt accumulation during the hybrid migration phase

Critical success factors

• Full-stack technical expertise with React and backend development capabilities

  • Deep understanding of React ecosystem design and modular architecture patterns

  • Ability to bridge frontend and backend requirements for seamless integration

• Modular architecture design

  • Sandboxed module architecture ensuring isolation and consistency

• Hybrid migration strategy

  • Incremental rollout approach minimizing service disruption

  • Parallel maintenance of legacy and new systems during transition

  • Clear integration points and compatibility layers between old and new architectures

Key results

• Successfully designed and implemented modular React ecosystem for profile page transformation

• Completed 1.5-year engagement transitioning from React expert to full-stack engineer role

• Successfully migrated profile page to React while maintaining 22M+ monthly active users

• Established foundation for complete platform transformation from Rails to React architecture