Archive: SYSLUME's earlier technical-decision work. Current focus: AI agents for SME back-office work → Order Intake

Fictional worked example · synthetic code

A boundary violation you can reproduce.

Question: can Billing read Workflow storage directly while the agreed architecture requires public module interfaces?

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The decision in one minute

Keep the modular monolith and repair the module boundary. In this synthetic example, a private import violates a declared rule. That finding alone does not justify a network service, a separate database or a rewrite.

Evidence	Interpretation	Limit
Billing imports workflow.repository.load_order	ARCH-001 is violated in the supplied source	Does not establish runtime impact
Corrected Billing imports workflow.api.order_total	The selected import boundary check passes	Behaviour equivalence needs separate tests
Independent deployment is not established by this example	Service extraction is not supported by this evidence alone	A verified isolation requirement could change the decision

1. Inspect the intentional violation

# demo/before/billing/invoice.py
from workflow.repository import load_order

ARCH-001 allows cross-module imports through api or contracts. Storage implementation belongs to its owning module.

2. Run the check

python scripts/check_architecture.py demo/before
# Expected: FAIL, ARCH-001, exit code 1

python scripts/check_architecture.py demo/after
# Expected: PASS, three files checked, exit code 0

python scripts/test_architecture_checks.py
# Negative and positive controls, including empty/invalid scope

Requires Python 3.10 or later. The checker uses the standard library and parses source; it does not execute the inspected application.

3. Inspect the correction

# demo/after/billing/invoice.py
from workflow.api import order_total

# demo/after/workflow/api.py
from workflow.repository import load_order

The storage import now stays inside Workflow. The supplied test suite also checks private import aliases, same-module imports, syntax failures, dynamic import mechanisms and empty scope.

4. Challenge the recommendation

If Billing needs verified independent release ownership or regulatory isolation, revisit the ADR and public contract. A local import rule cannot settle that broader decision. Do not disable a failing gate to avoid discussing the changed requirement.

What this does not prove

This Python-layout-specific static check does not validate SQL writes, re-export safety, runtime dependencies, API compatibility, deployment topology or security. The CI workflow is provided for reuse; the current evidence is a local run, not a hosted CI certification.

From an example to your decision

A scoped review starts with your constraints and evidence. The check shown here is a demonstration; applying equivalent controls to another repository or language needs an agreed adapter and acceptance criteria.

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