Taming a monolith: modularising SIMATIC AX
Siemens AG · SIMATIC AX · Jan 2023 – Mar 2025
The Situation
Siemens was building SIMATIC AX, a next-generation automation engineering platform. One team was working on a single, massive codebase. Build times had crept past 30 minutes. The team had tried everything to speed up the builds, but nothing stuck.
The Real Problem
Everyone was focused on making the builds faster. More caching, more compute, different bundlers. But nobody was asking the bigger question: why is everything in one place to begin with?
Working closely with the Chief Architect and Chief Product Owner, I stepped back and looked at the big picture. The codebase had grown organically, with different functional areas tangled together in ways that made incremental builds impossible. The problem wasn't the build tool. It was the architecture. The code needed to be analysed, taken apart, and reorganised into separate, independent modules.
Key Decisions
- Analysed and modularised the codebase. I mapped the various parts of the application, identified the natural boundaries, and separated them into isolated repositories. Each module got its own codebase with clear ownership and independent build pipelines. This was the fundamental shift that made everything else possible.
- Introduced microfrontend architecture. This was new territory for the team. I trained them on the principles, established contracts between modules, defined communication patterns and deployment boundaries. The team went from a monolithic mindset to thinking in independently deployable units.
- Created a pattern library as the shared foundation for UI consistency across all the newly separated modules. Instead of each team reinventing components, they pulled from documented, tested patterns.
Build times dropped from 30+ minutes to under 5 minutes. But that was just the measurable result. The bigger impact was strategic. The platform went from one team struggling with a monolith to multiple teams working independently on well-defined modules. Each team could deploy on their own schedule. The architecture could scale with the organisation.
The Exit
Two-year engagement spanning January 2023 to March 2025. The modular architecture, microfrontend patterns, and pattern library were fully documented and handed off to the internal teams. The team was trained and equipped to evolve the architecture on their own.
Facing something similar?
Every situation is different but the patterns repeat. If your team is stuck, your architecture is uncertain, or you're about to make a big technical bet, tell me what's going on.