Interface FeaturesDBInstance

Every record of one layer, via the composed key — no secondary index needed.

Records in a given sync state, across every layer.

Writes a pulled batch in ONE transaction, skipping every record that holds unsynchronised local work.

🛑 The rule lives here, and not in the caller, because get and put above open SEPARATE transactions: reading the state in the orchestrator and writing after it would leave a window in which the optimistic write lands between the two — and property 1 of the sync contract ("a capture never silently disappears") would hold only by timing.

A record is skipped when it already exists with syncState !== "synced" (preserved), or when it is synced and the source serves it under the very marker already stored (unchanged). Everything else is inserted or rewritten.

tombstones are entities the source served as DELETED: never written, their stored copy is removed when it is synced (removed) and kept when it holds local work (preserved) — in the same transaction, under the same identity resolution.

⚠️ Each record carries the source that served it (sourceKey). A copy another source served is never unchanged — it is rewritten, and becomes this source's — and a tombstone never removes it: that source's deletion says nothing of this one's rows.

Removes, in ONE transaction, every record of layerId that keep does not name, is synced, and carries a server identity — what a complete pull did not return.

🛑 Local work is never removed, and neither is what has no server identity. A record holding an unsynchronised capture is not synced; an entity created here has no row to be absent from. The state is read in the same transaction as the removal, for the reason putManyPreservingLocal gives: an optimistic write must not slip between the two.

⚠️ With sourceKey, only that source's records are candidates, and those written before records carried one: what another source served on a layer of the same id is not this pull's answer to judge. Without it, every record of the layer is, as before.