Reverse ETL Documentation Template

Every practical result for reverse ETL documentation is a vendor's own product docs: Census, Hightouch, Fivetran, and the smaller platforms. Each covers the same three things, a source query, a destination object, and a field mapping with a sync mode. Hightouch's own HubSpot guide names the risk: its default field behavior, Always sync, writes the model's value on every run, including nulls, and can erase existing production data. The safer option sits on the same page, and Fivetran ships an equivalent under a different name. No vendor page inventories which fields need it.

So Conflict and Overwrite Rules is that inventory. Anything a human can also edit in the destination gets its real edit history pulled for sixty to ninety days, a count rather than a guess. That count decides one of three policies: write only when the destination field is empty, let the newer timestamp win, or remove the field from the mapping and pull it into the warehouse one way instead. A field nobody but the warehouse ever touches keeps the sync's default.

Northfield Systems, a fictional B2B SaaS company, syncs 28 fields into HubSpot's Company object hourly. Twenty-one are pure telemetry. The other seven are also edited by revenue operations, and all seven sat on the Always sync default: 96 human edits logged over 60 days, every one reverted by the next hourly run, 28 minutes later on average. Reclassifying the seven moved 62 of those 96 edits onto a policy that makes overwrite structurally impossible and the other 34 onto one where only a genuinely fresher value wins.