Define a stable event key and conflict policy before repeated data deliveries reach a machine-record database.
Define the stored identity
PostgreSQL documents INSERT conflict handling against uniqueness constraints. A stable application key can distinguish a repeated write from a new stored record. Primary reference: INSERT ON CONFLICT.
This capability does not choose the right event identity for a project. Nor does one protected database row automatically make every associated notification or external action idempotent. Keep the actual storage boundary explicit.
A hypothetical repeated import
Imagine an observation carries producerP, runR and event 17. A reconnect causes the same identified observation to be imported twice. Under an agreed unique composite key and duplicate policy, the stored event can remain one row. Two distinct observations with equal values should instead have distinct identities and remain two rows.
Now imagine the same key arrives with a different payload. Silently discarding one would hide a possible identity or data-integrity problem. The project should specify that conflict outcome rather than treating every uniqueness conflict as a harmless repeat. These examples prescribe no production database schema.
Review the end-to-end effect
Record event-key scope, producer/run lifetime, missing-key handling, duplicate definition and differing-payload response. Ask when a stored row is considered committed and which downstream effects can repeat independently. Preserve receipt evidence separately if the project needs a delivery audit.
This guide executes no SQL or machine command and claims no HM database implementation. A useful acceptance example includes identical repeats, equal-valued new events and conflicting payloads for one key. The review should establish the intended durable record effect rather than assuming that choosing a transport delivery level automatically defines correct storage.
Customer Questions
Are equal measurements necessarily one event?
Retain event identity.
Is every uniqueness conflict harmless?
Different payloads need a defined response.
Does one row protect all external effects?
Review each effect boundary.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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