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  • Appnetwise
  • Last Updated2/3/2025

Self-Contained Systems: A Modern Approach to Software Architecture

In the ever-evolving landscape of software architecture, while microservices have dominated discussions for over a decade, alternative architectural patterns have emerged to address their limitations. One such approach is Self-Contained Systems (SCS), first documented by Stefan Tilkov and other architects at scs-architecture.org.

The Microservices Misconception

When tech giants pioneered microservices around 2010, everyone wanted to copy their success. But here's the catch: breaking an application into tiny pieces doesn't automatically make it better.

Think of it like this: If you have a messy room, cutting it into smaller rooms doesn't solve the problem—it just gives you many messy rooms to manage. The same goes for software. Many teams ended up with what we now call a "distributed mess": too many services, too few developers, and plenty of headaches.

The lesson? Size isn't everything. What matters is building services that make sense for your team and business. Sometimes bigger, well-organized services are better than many tiny ones.

Key Takeaway: Focus on what works for your team, not what worked for Netflix or Amazon. Your architecture should match your resources and needs.The Hidden Costs of Microservices

While microservices promise flexibility and scalability, they come with significant challenges:

  1. Communication overhead through synchronous API dependencies
  2. Increased latency and failure risks inherent to distributed systems
  3. Complex debugging requiring sophisticated distributed tracing
  4. High maintenance burden due to inter-service dependencies



Enter Self-Contained Systems

Self-Contained Systems (SCS) offer a middle ground between monolithic applications and microservices. Think of them as autonomous business units that include everything from the user interface to the database. They're larger than typical microservices but more focused and manageable than monoliths.

Key Characteristics of SCS:

  • Complete vertical slices of functionality
  • Independent data storage for each system
  • Minimal synchronous communication between systems
  • Event-driven architecture for data sharing
  • Team ownership of entire features


Real-World Success: 

Many organizations have successfully modernized their legacy systems using the SCS approach. Instead of breaking systems into dozens of tiny microservices, they create focused, self-contained business units that can evolve independently.

Key Benefits:

  • Teams own their complete stack (UI to database)
  • Changes can be made safely and incrementally
  • Systems communicate through simple events
  • Each unit scales based on its actual needs

This approach has consistently shown measurable improvements in deployment speed and team efficiency, with many organizations reporting significant reductions in coordination overhead and faster time-to-market for new features.



    Implementation Strategies

    When considering SCS implementation, remember these key points:

    1. Start Gradually: Use the Strangler Fig Pattern to replace parts of your system incrementally rather than attempting a complete rewrite.
    2. Focus on Data Independence: While systems may need to share data, use messages / events rather than real-time API calls. For example, product information doesn't need to propagate instantly across all systems.
    3. Maintain Clear Boundaries: Share technical components (like UI libraries) but keep business logic within each system.
    4. Embrace Event-Driven Communication: Use message brokers like Kafka or ActiveMQ for inter-system communication instead of synchronous APIs.


    Is SCS Right for Your Organization?

    SCS might be particularly suitable if:

    • You have distinct business domains that operate independently
    • Different parts of your system have varying scalability needs
    • You want to modernize your system incrementally
    • Your teams can own and maintain full-stack features
    • Real-time consistency isn't critical for all operations

    Conclusion

    While microservices have their place, Self-Contained Systems offer a pragmatic alternative that might better suit many organizations. They provide the benefits of modularity without the extreme complexity of fine-grained microservices. The key to successful software architecture isn't following trends—it's choosing the right level of modularity for your specific business context.

    Remember: The goal isn't to be either monolithic or micro; it's to create maintainable, scalable systems that serve your business needs effectively. SCS might just be the sweet spot you've been looking for.

    For more information about Self-Contained Systems, refer to: