Day-0 Guide
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Chapter 06 of 13DAY-0

Day-0 is not an empty starting database

By the time Metrolane reaches Day-0, the company already has a history. Customers exist. Orders exist. Invoices exist. Documents exist.

Source systems contain different views of the enterprise. Named scenarios already stand.

Day-0 freezes that prepared company into a reproducible reference estate.

Understand

Build first. Freeze later.

Conceptually:

  1. 1build source systems
  2. 2seed business history
  3. 3run integrations
  4. 4ingest source data
  5. 5build canonical enterprise
  6. 6verify scenarios
  7. 7validate invariants
  8. 8FREEZE DAY-0

Day-0 is meaningful because all of that work has already happened.

What Day-0 is

  • a deterministic reference estate
  • a known opening state
  • a permanent basis for exploration
  • a starting authority for runtime reset
  • a reproducible point for verification

What Day-0 is not

  • a live operations dashboard
  • an empty company
  • an arbitrary snapshot of today
  • a mutable simulation database
  • a view where every system is perfectly synchronized
See it in Metrolane

An intentional lag

SCN-X04 · Won deal order lag

At Day-0:

CRM Opportunity OPP-2026-900006 · CLOSED_WON

expected handoff

ERP Sales OrderNot present at Day-0

The missing downstream order is not hidden.

It is part of the prepared enterprise state.

Why freeze an imperfect state?

Because realistic enterprise states are often interesting precisely because systems are not perfectly synchronized.

A useful Day-0 can contain:

lagsduplicatesmismatchespending index statesdifferent source representationsexpected-but-absent downstream records

The key requirement is not perfection. It is that the state is intentional, explainable and reproducible.

Named scenarios

Metrolane's Day-0 scenarios describe deliberately prepared enterprise conditions.

Examples include:

HR hire → ERP employee lagTermination access lagCRM duplicate accountWon deal order lagRetail stock mismatchFranchise offline syncProduction dispatch lagQuality release lagIoT/MES event orderingWarranty fulfillment lagPOD acknowledgement lagDelivery/receipt lag

The public Day-0 meaning is Standing at Day-0 — not a runtime status.

Important distinction

Scenario is not a canonical business entity

A scenario is a compiled explanatory/read-model concept built from:

  • scenario definition
  • verified predicate
  • stable evidence anchors
  • actual Day-0 records

There is no need to invent a fake canonical Scenario row merely to show it in the UI.

See it in Metrolane

Completed vs incomplete

Compare:

Completed
OPP-2026-900001

SO-2026-000001
Day-0 lag
OPP-2026-900006

expected

ERP Sales Order absent
Go deeper
Why Day-0 matters later

A frozen reference estate enables:

repeatable testsreproducible Explorer buildsruntime RESETreplay comparisonscenario verificationdata-quality gatesstable demosarchitecture debugging

Without a stable baseline, two simulator runs could differ simply because they started from different enterprise states.

Chapter takeaway

  • Day-0 is a prepared, verified and frozen enterprise.
  • It already contains history and intentional imperfection.
  • Scenarios make those interesting states explicit.
  • The frozen estate becomes the reference authority for exploration, reset and replay.