Extension-based architecture for legacy RPA modernization

This post is a quick overview of an Abto Software portfolio case study on extension-based architecture for legacy RPA modernization.

Robotic process automation update without rebuild – a smart SAP integration

Project overview

Our customer is a large enterprise operating in a fast-paced business environment where automation plays a critical role. Over the years, they had built a powerful robotic process automation (RPA) platform that supported core operational workflows. However, the system was based on a classic monolithic architecture, which had become increasingly difficult to maintain.

While the platform continued to process mission-critical workflows, it struggled to keep up with modern requirements. New APIs were difficult to integrate. SDK updates often caused compatibility problems. Even small changes required extensive testing and full re-releases of the application.

From a technical standpoint, the system was showing clear signs of aging. From a business perspective, it was becoming a liability.

Maintenance costs were rising sharply. In fact, the annual cost of maintaining the legacy system was approaching the original development cost. The client also faced a shrinking pool of developers familiar with the outdated stack. Security vulnerabilities were harder to patch. Bugs were difficult to trace and often appeared in unrelated parts of the system.

Despite these challenges, a full rewrite was not an option. The platform was deeply embedded in daily operations, and any major disruption could cause serious business losses. The client needed a modernization strategy that would preserve the existing system while extending its capabilities.

That is where Abto Software stepped in. Drawing from our experience in legacy modernization and RPA development, we proposed a solution that would modernize the platform without tearing it apart.

Main goals

The primary objective was clear: modernize the existing monolithic system without rebuilding it from scratch. However, achieving that goal required a carefully balanced technical approach.

We worked closely with the client to define a set of concrete goals that would guide the solution design.

The modernization effort needed to enable:

• Support for new APIs and SDKs without destabilizing the existing system
• Integration with modern platforms, especially SAP, which played a central role in business workflows
• Lower operational risks by avoiding unintended side effects in legacy components
• Higher productivity, allowing teams to fix bugs and add features without triggering full application re-releases

Another critical requirement was minimizing downtime. The client could not afford service interruptions or workflow failures during the transition.

In other words, this was not just a technical upgrade. It was a strategic transformation aimed at extending the lifespan of a valuable legacy product.

Instead of rewriting the entire platform, our approach focused on extension-based modernization. This allowed new functionality to be added alongside existing logic, rather than embedded directly into it.

This philosophy aligned perfectly with Abto Software’s expertise in incremental modernization, where stability and business continuity come first.

How the solution works

The problem

At its core, the system was designed to create and manage workflow templates. Each workflow consisted of predefined steps responsible for tasks such as:

• Data synchronization
• File processing
• Smart analytics
• Email notifications
• Report generation

All of these steps were implemented inside a single, tightly coupled application.

While this approach worked initially, it became a serious limitation over time. Any change to one workflow step had the potential to affect others. Even minor updates could introduce unexpected side effects.

As the system evolved, these risks multiplied. Updates often caused workflow disruptions, leading to operational delays and frustrated users. Testing became more complex and time-consuming with each release.

The most significant pain point was SAP integration. SAP-related workflows required frequent updates, but modifying them inside the monolith was risky and slow.

Our solution

To address these issues, Abto Software designed and delivered a standalone application dedicated to SAP-related workflow steps.

Instead of modifying the legacy codebase, we introduced a flexible extension-based architecture, inspired by the Visual Studio Code extension model. This architectural pattern allows functionality to be added as independent modules rather than hard-coded changes.

Each extension operates as a separate unit with:

• Its own logic
• Its own lifecycle
• Its own process boundary

Now, new SAP-related features are introduced as independent extensions, not as modifications to the monolith itself.

This approach fundamentally changed how the system evolves. Updates no longer interfere with existing workflows. New features can be tested, deployed, and maintained independently.

From our practical knowledge, this model significantly reduces the risk of regression while dramatically improving development speed.

Our contribution

Abto Software played a central role in designing and implementing the modernization strategy. Our contribution covered architecture design, development, testing, and integration.

Specifically, our team:

• Built a standalone application responsible for handling SAP-related workflow steps
• Designed and implemented a fully extension-based model
• Added a workflow catalog to the legacy system to enable dynamic workflow discovery and execution
• Created an IPC (Inter-Process Communication) layer using standard input/output streams
• Defined consistent RPC endpoints to ensure uniform interaction between workflow steps
• Developed robust integration tests to guarantee backward compatibility

This work ensured that the legacy system could evolve without losing stability or reliability.

As indicated by our tests, the new architecture allowed SAP workflows to be updated independently while maintaining seamless interaction with existing components.

This project demonstrates how legacy RPA platforms can be modernized safely and efficiently. Instead of fighting the monolith, we worked around it—extending its capabilities without compromising its core.

Main challenges

Making a monolith extensible

The first major challenge was architectural. The original system was never designed with modularity in mind. Every component was tightly coupled, making isolation difficult.

Introducing extensions without causing failures required careful refactoring. We needed to create extension points without destabilizing existing logic.

We addressed this challenge by:

• Refactoring parts of the legacy application to support external extensions
• Converting SAP-specific logic into a standalone extension-based application
• Implementing comprehensive integration tests to validate backward compatibility

Through trial and error, we discovered that process isolation was key to minimizing risk.

Bridging technologies

Another challenge was technological mismatch. The new SAP handler was built using modern technologies that were not natively compatible with the legacy system.

Direct integration was not feasible without introducing dependencies that could compromise stability.

Our solution was to fully decouple the SAP handler from the monolith by running it as a separate application.

To enable communication, we:

• Used standard input/output streams for data exchange
• Introduced a dedicated communication layer
• Implemented a clean IPC-based interaction model

This approach ensured smooth interoperability while keeping both systems independent.

Based on our observations, this design significantly reduced integration complexity and future-proofed the platform.

Tools & technology stack

Frameworks:

.NET 6.0

Platforms:

SAP

Architecture:

• IPC
• RPC

Patterns:

• Contribution points
• Process isolation

Value delivered to business

Before modernization, the client faced a system that was becoming increasingly unreliable and expensive to maintain. After implementing the extension-based architecture, the situation changed dramatically.

From a business standpoint, the value delivered was immediate and measurable.

Increased savings

Extensions are reusable across products within the same domain. This reduced duplicated development efforts and lowered long-term costs.

Reduced complexity

By separating SAP-related functionality into independent extensions, maintenance became simpler. Troubleshooting is now faster and more precise.

Greater flexibility and scalability

New features can be added without major changes to the core system. The platform is now prepared to evolve alongside business needs.

Better stability

Perhaps most importantly, new features no longer threaten legacy components. Each extension runs independently, preserving system reliability.

Our investigation demonstrated that extension-based modernization is one of the safest ways to extend the life of legacy RPA platforms.

Conclusion

This project highlights how legacy RPA systems can be modernized without costly rebuilds or operational disruption. By adopting an extension-based architecture, the client gained flexibility, scalability, and stability—all while preserving their existing investment.

From team point of view, this approach represents a practical path forward for enterprises facing similar challenges. Based on our firsthand experience at Abto Software, extension-driven modernization delivers real, long-term value.

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FAQs

1. Why not rebuild the RPA system from scratch?

A full rebuild would have been costly, risky, and disruptive. Extension-based modernization allowed incremental improvements without downtime.

2. What makes extension-based architecture safer?

Extensions operate independently, reducing the risk of unintended side effects in legacy code.

3. How does this approach support SAP integration?

SAP logic is isolated in standalone extensions, making updates faster and safer.

4. Can this model be reused for other integrations?

Yes. The same architecture can support additional platforms and workflows.

5. Is extension-based modernization suitable for all legacy systems?

While not universal, it works especially well for workflow-driven and RPA platforms.

6. What role did Abto Software play in this project?

Abto Software designed the architecture, developed the solution, and ensured seamless integration and testing.