Distributed Architecture

Up to this point, we have described a software product as a structured realization of a business process. That description already implies something important: the product is not a single monolithic program, but a composition of independent parts.

This page explains why that structure naturally leads to a distributed architecture.

Distribution is not a technical goal by itself. It is a consequence of independence.

What We Already Know

From the previous chapters, we can rely on several established facts:

• A software product is a set of use cases, and each use case can be implemented independently.
• There is a special application use case that coordinates the overall business process flow.
• Different kinds of logic exist (state logic, business logic, data processing logic, data access logic), and each has a distinct responsibility.
• A non-functional architecture exists to support, not define, business behavior.

Together, these facts describe a product composed of independent functional components, supported by shared infrastructure.

Independence Leads to Distribution

When components are truly independent, they can be:

• Designed independently
• Implemented independently
• Tested independently
• Deployed independently

Independent deployment is the key point. Once deployment independence is possible, distribution becomes a design option.

At this moment, a software product can be viewed as a set of services communicating over a network—whether that network is local or global.

Different Ways to Distribute

Because functional components are independent, they can be grouped and deployed in different ways, depending on operational needs.

For example, components may be grouped:

• By architectural layer (state logic services, business logic services, etc.)
• By use case (each use case deployed as its own service)
• By a hybrid of both approaches

No single grouping is universally correct. The important point is that the architecture allows these choices without redesigning business functionality.

The Minimal Deployment Unit

A deployable service rarely contains a single class or function. Instead, it forms a minimal, coherent unit that includes:

• One or more use case components
• The application use case component
• Required non-functional infrastructure components

Such a unit represents a meaningful fragment of the business process that can operate independently in a distributed environment.

What Makes This Possible

This level of flexibility is only possible when the product is structured deliberately:

• Use cases are clearly identified
• Logic layers have strict responsibility boundaries
• Business components are unaware of infrastructure details
• Infrastructure is designed to support distribution natively

When these conditions are met, distributed architecture is not a risky transformation—it is a natural extension of the design.

A distributed system is not created by adding network calls. It emerges when independence is taken seriously.

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