Why Self-Contained Systems Might Replace Microservices: Key Differences Explained

What is SCS (Self-Contained Systems)

SCS is an architectural approach that splits a large system into many independent, cooperating systems. Its characteristics include:

Autonomy : each SCS is a self‑contained web application with its own data, logic and UI.

Single team : one team owns a SCS and has final say over its code base.

Asynchronous dependencies : communication with other SCS or third‑party systems should be asynchronous, allowing the SCS to keep working even if the other system is offline.

Optional API : a SCS may expose a service API, but it also has its own UI for direct user interaction.

Own data & logic : both data storage and business logic reside inside the SCS.

Own UI : the UI is part of the SCS and is not shared with other systems.

No shared business logic : business code is not shared between SCS; common libraries may be used.

Minimal shared infrastructure : shared resources such as a single database are avoided; if used, each SCS should have its own schema or model.

SCS vs Microservices

Both share concepts like isolated deployable units and technology‑agnostic choices, but key differences are:

Granularity: microservices are smaller; an SCS can be large enough for a whole business module.

Number of services: a system may have hundreds of microservices but only 5‑25 SCS.

Communication: microservices freely call each other; SCS aim to avoid direct calls, preferring asynchronous integration.

UI: each SCS includes its own UI, while microservices may separate UI from logic.

Integration: SCS integration happens mainly at the UI layer; microservices integrate at the logical layer via APIs.

In practice an SCS can be further broken down into microservices, making it a specific micro‑architecture.

Conclusion

After comparing SCS with microservices, the main take‑aways are:

SCS are larger in scope than typical microservices.

Fewer SCS are needed to cover a domain.

Asynchronous communication (e.g., enterprise bus) is preferred.

Each SCS owns a complete UI and business functionality.

Integration is often done via front‑end components or a small piece of JavaScript.