Azure Cosmos DB geospatial lookup consuming too high RU - azure

Question

I have a single Azure Cosmos DB collection I am querying against, hoping to use Geo-spatial index for efficient queries. The problem I'm encountering is that the RU consumption seems inefficient.
The collection has only 50k 1kb documents in it, but a query using ST_DISTANCE returning a single document consumes >900 RUs.
I've seen the RUs scale linearly based on the # of documents in the collection. It would seem indexing should prevent this behavior.
Example Query (950 RUs):
SELECT * FROM c where ST_DISTANCE(c.location, { 'type': 'Point', 'coordinates': [34.69, -1.91] }) < 500
Example document:
[
{
"id": "1504891036",
"name": "Oujda",
"location": {
"type": "Point",
"coordinates": [
34.69,
-1.91
]
},
"population": 409391,
"country": "Morocco",
"country.iso2": "MA",
"country.iso3": "MAR",
}
]
I've not modified the default indexing policy, which seems to cover spatial indexing:
{
"indexingMode": "consistent",
"automatic": true,
"includedPaths": [
{
"path": "/*",
"indexes": [
{
"kind": "Range",
"dataType": "Number",
"precision": -1
},
{
"kind": "Range",
"dataType": "String",
"precision": -1
},
{
"kind": "Spatial",
"dataType": "Point"
}
]
}
],
"excludedPaths": []
}

Answer 1

I determined the problem. I had transposed the longitude and the latitude coordinate prescribed by GeoJSON:
Cosmos is expecting:
"location": {
"type": "Point",
"coordinates": [
<#lon>,
<#lat>
]
I had assumed, incorrectly, that it was lat/lon. Therefore many of my latitudes were outside of the 90/-90 range required, since longitude can be 180/-180. After re-creating my ~50k documents, RU for coordinate based lookups are consistently <10 RUs.
Before fix (all docs have transposed lat/lon coordinates, many outside the 90/-90 bounds and therefore invalid):
SELECT * FROM c where ST_DISTANCE(c.location, { 'type': 'Point', 'coordinates': [34.69, -1.91] }) < 500
940 RUs, 1 document returned
After fix (all docs re-created with lat/lon set correctly per GeoJSON specs):
SELECT * FROM c where ST_DISTANCE(c.location, { 'type': 'Point', 'coordinates': [-1.91,34.69] }) < 500
6 RUs, 1 document returned
Initial issue was confirmed/diagnosed by the following query:
SELECT ST_ISVALIDDETAILED(c.location) FROM c where c.name = "Kansas City"
Error: "Latitude values must be between -90 and 90 degrees."