Snapshot Drift

The same historical snapshot can produce a different result after rebuild.

A month-end or quarter-end snapshot may be rebuilt from mutable source history long after the original report was published.

If source records, dimensions, business logic or visibility cutoffs have changed, the rebuilt result can differ from the original even though the reporting date is identical.

Without explicit drift detection, teams may discover these differences only after an audit, reconciliation failure or user complaint.

The original March snapshot contains 1.250 contracts. A later rebuild contains 1.286.

Compare the original result, an unexplained rebuild and a controlled restatement.

Snapshot drift compares two executions of the same historical reporting contract.

The original snapshot and the rebuilt snapshot must use the same reporting date, source cutoff, dimension perspective and business logic before their results can be compared meaningfully.

Historical inputs and reporting logic continue to change after publication.

Source systems can correct past transactions, reload dimensions or deliver late-arriving records. Engineering teams can also change joins, filters and calculation logic.

A later rebuild sees this newer world unless the original knowledge and execution context were preserved.

Preserve the inputs and execution context required for reproducibility.

snapshot_date
source_cutoff
knowledge_cutoff
logic_version
dimension_version
published_at
row_count
control_total

Detect and explain every difference between original and rebuilt output.

Snapshot drift separates reproducibility failures from legitimate restatements.

Not every difference is wrong. A corrected or restated report can be valid, but it must not silently replace the historical output users originally received.

Drift analysis explains whether a difference comes from source corrections, changed logic, dimension leakage or an approved restatement.

This protects trust in historical KPIs and makes reporting changes auditable.

How Snapshot Drift connects to other historical patterns

Snapshot drift is the failure mode that appears when historical reconstruction, correction handling and reporting cutoffs are not controlled together.