One pattern at every scale.
The architecture · Structure 2 / 5
One pattern repeats at every scale of the system. Build small parts with stated contracts. Declare an assembly of them as a document. Let a runtime turn that document into the running thing. Wherever this pattern is followed, the result can be inspected, versioned, generated, reviewed, and replaced.
The same shape at four scales
Interfaces
Primitives compose into sections, sections into declared views, views into an application. A screen is a document about parts, not a hand-assembled artifact.
Services
Shared libraries carry the crosscutting behavior once, domain services declare what they expose, and clients are generated from those declarations. Nothing hand-writes the seam between two services.
Deployments
A workload is packaged as a configurable unit, and where it runs is a separate declaration of desired state. Placement, promotion, and rollback become edits to a document rather than acts of operation.
Procedures
Repeatable work, whether performed by a person or delegated to software, is packaged as a portable procedure with its own inputs, tools, and checks. Practice becomes an artifact instead of folklore.
Why declarations beat instructions
They can be read by anything
People, tooling, and agents can all inspect a declaration, which is what makes a system explainable at scale.
They can be diffed
Change becomes visible as change rather than as a new state that appeared.
They can be generated
When the shape is data, tooling can produce, validate, and migrate it in bulk, so a fleet-wide correction is a program rather than a campaign.
They can be reversed
A previous declaration is still a valid declaration, which is the simplest possible rollback story.
The discipline this requires
Composition only pays if the parts stay honest: one job each, a stated contract, no private back channels between them, and a real deprecation path when a contract has to change. Where those slip, composition degrades into a large system with extra indirection. The governance of contracts is what keeps the discipline from depending on who happens to be reviewing.