Domain model

Use UUID primary keys internally. Human-facing references are immutable unique strings.

User

id
public_ref (USR-...)
display_name
role: operations_manager | rental_employee
active

Customer

id
public_ref (CUS-0001)
first_name, last_name
email, phone
postal_code, city
date_of_birth (optional)
merged_into_customer_id (optional)
created_at, updated_at

Vehicle

id
public_ref (MO-001)
make, model, model_year
registration_number
location
operational_status: available | rented | cleaning | maintenance | blocked
odometer_km
next_service_km
active
version for optimistic concurrency

Booking

id
public_ref (BK-...)
customer_id, vehicle_id
starts_at, ends_at
status: reserved | active | returned | cancelled | blocked
start_odometer_km, end_odometer_km
requirements_complete

Database invariant: active/reserved bookings for the same vehicle may not overlap after validation. A deliberate seeded conflict may be imported as an external-data quality issue through a controlled bypass, never created through the normal command API.

Inspection

id
public_ref
booking_id, vehicle_id
type: checkout | return
fuel_level_percent
cleanliness_ok
damage_reported
technical_warning
notes
odometer_km
completed_at, completed_by

MaintenanceRecord

id
vehicle_id
occurred_at
odometer_km
category
summary

DataQualityIssue

id
public_ref
rule_type:
- possible_duplicate_customer
- missing_required_field
- odometer_regression
- booking_overlap
- vehicle_status_conflict
entity_type, entity_id
severity: low | medium | high
status: open | deferred | resolved | rejected
evidence_json
proposed_action_json
detected_at, resolved_at, resolved_by

OutboxEvent / WorkflowRun

id / event_id
event_type
aggregate_type, aggregate_id
payload_json
occurred_at
delivery_status: pending | delivering | succeeded | failed
attempts, next_attempt_at, last_error
external_run_id

AuditEvent

id
actor_type: user | service | system
actor_id / actor_label
action
entity_type, entity_id
correlation_id
before_json, after_json, metadata_json
occurred_at

Required invariants

a vehicle return cannot reduce the canonical odometer;
a return with a lower submitted reading is recorded as an inspection and issue, while canonical odometer remains unchanged;
damage or a critical warning blocks the vehicle;
merged customers remain as tombstones linked to the survivor;
resolving a quality issue and applying its correction is transactional and audited;
public references never change after creation.

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