A dispatch coordinator in York needs packed parcels that still lack a tracking number before the carrier arrives. These five synthetic shipments include an omitted field, an explicit null, an already labelled parcel, another depot, and a dispatched parcel. Adding tracking must remove only the newly labelled parcel from the exception list.

Start with a running Elasticsearch-compatible endpoint and an unused field_note_parcels index. The client is curl; run exactly the same commands on each server, changing only ES (http://localhost:19200 for Elasticsearch, http://localhost:9200 for the gateway).

ES=http://localhost:19200
curl -fsS -X PUT "$ES/field_note_parcels" \
  -H 'Content-Type: application/json' -d '{"mappings":{"properties":{"contents":{"type":"keyword"},"depot":{"type":"keyword"},"carrier":{"type":"keyword"},"status":{"type":"keyword"},"tracking":{"type":"keyword"}}}}'

curl -fsS -X POST "$ES/field_note_parcels/_bulk?refresh=wait_for" \
  -H 'Content-Type: application/x-ndjson' --data-binary @- <<'NDJSON'
{"index":{"_id":"parcel-101"}}
{"contents":"Ceramic mugs","depot":"York","carrier":"Parcel North","status":"packed"}
{"index":{"_id":"parcel-102"}}
{"contents":"Cotton towels","depot":"York","carrier":"City Express","status":"packed","tracking":null}
{"index":{"_id":"parcel-103"}}
{"contents":"Desk lamps","depot":"York","carrier":"Parcel North","status":"packed","tracking":"PN-103"}
{"index":{"_id":"parcel-104"}}
{"contents":"Plant pots","depot":"Leeds","carrier":"Parcel North","status":"packed"}
{"index":{"_id":"parcel-105"}}
{"contents":"Wool blankets","depot":"York","carrier":"City Express","status":"dispatched","tracking":"CE-105"}
NDJSON
sleep 5

Both servers get the same five-second settling pause after each write phase. Search the packed York parcels with no indexed tracking value:

curl -fsS -X POST "$ES/field_note_parcels/_search" \
  -H 'Content-Type: application/json' -d '{"size":10,"query":{"bool":{"filter":[{"term":{"depot":"York"}},{"term":{"status":"packed"}}],"must_not":[{"exists":{"field":"tracking"}}]}}}'

Expect exactly parcel-101 and parcel-102, with their complete sources and a total of 2. An omitted field and JSON null both fail exists; an empty string would count as present, so ingest unknown tracking as null or omit it.

Count that same exception list by carrier:

curl -fsS -X POST "$ES/field_note_parcels/_search" \
  -H 'Content-Type: application/json' -d '{"size":0,"query":{"bool":{"filter":[{"term":{"depot":"York"}},{"term":{"status":"packed"}}],"must_not":[{"exists":{"field":"tracking"}}]}},"aggs":{"carriers":{"terms":{"field":"carrier","size":10}}}}'

Expect Parcel North: 1 and City Express: 1, with no hits because size is zero. Assign the first parcel’s tracking number and read it back:

curl -fsS -X POST "$ES/field_note_parcels/_update/parcel-101?refresh=wait_for" \
  -H 'Content-Type: application/json' -d '{"doc":{"tracking":"PN-101"}}'
sleep 5
curl -fsS "$ES/field_note_parcels/_doc/parcel-101"

The update returns updated. The read must preserve Ceramic mugs, York, Parcel North, and status: packed, adding only tracking: PN-101. Repeat the search and facet commands: only parcel-102 remains, the total is 1, and only City Express: 1 remains in the buckets. This records a label assignment, not proof of carrier collection.

The fixture, replay, and recorded run verify identical requests, HTTP and bulk statuses, IDs, every source, totals, and carrier counts. Elasticsearch 8.15.0 and gateway 0.2.0 at 7e56704, backed by Qdrant 1.15.5 in default embedded-source mode with synchronous writes, passed 66/66 checks. No gateway code changed; this five-record check makes no performance claim.

Boundary: refresh timing guarantees and atomic concurrent updates remain outside the gateway’s supported semantics.

Remove only this example’s index when finished:

curl -fsS -X DELETE "$ES/field_note_parcels"