The method
Represent quantities as exact decimals and monetary amounts as integer minor units. Bind each event identifier to its kind and canonical payload. Return the previous result for an identical retry and reject the same identifier when its details change.
Use transactions for receipt posting and paired transfers so a failure cannot leave half an operation committed. Preserve human-entered events across imports and block unresolved units from creating stock movements.
Keep historical purchases separate from present stock, and observation time separate from the period being reported. Record failed collection, stale coverage and unknown amounts explicitly rather than silently treating them as zero.
What the work shows
Implemented ledger mechanisms preserve unknown stock until a physical count establishes a baseline. Duplicate receipt controls, payload-bound retries and rollback tests address different ways quantities or money could be counted twice.
The meaning of a record still matters after the arithmetic is correct. Recording a payment allocation does not move money or independently reconcile a bank account. An atomic transfer record does not prove physical arrival.
Interpretation and limits
The implementation supports bounded local operations, not every accounting or inventory process. Partial deliveries, in-transit stock and auditable reversals require their own workflows and acceptance checks.
The next test
Use synthetic records to exercise ambiguous units, retries, late events and partial failures. Develop correction and reconciliation procedures before expanding automation, with a clear owner for each unresolved record.