Index on array field not being effective - mongodb

Question

I have the following collection, with around 600 entries, that represents cooking recipes:
"name":"",
"ingredients":[]
"steps":""
"dificulty:""
}
The items inside the ingredients array have the following structure
"id":"",
"name":""
}
Some recipes are more demanding and can have an array of 20+ ingredients.
When doing a .find("ingredients.id":"12345") to get the results takes me almost 7/8 seconds.
Meanwhile created an index for the field but the loading time keeps the same.
{
"ingredients.id" : 1
}
Checked the "explain" tab on the mongo dbcompass and it confirms that the created index is being used.
the IXSCAN shows:
{
"stage": "IXSCAN",
"nReturned": 28,
"executionTimeMillisEstimate": 0,
"works": 29,
"advanced": 28,
"needTime": 0,
"needYield": 0,
"saveState": 0,
"restoreState": 0,
"isEOF": 1,
"keyPattern": {
"ingredients.id": 1
},
"indexName": "recipes_ingredients _id",
"isMultiKey": true,
"multiKeyPaths": {
"ingredients.id": [
"ingredients "
]
},
"isUnique": false,
"isSparse": false,
"isPartial": false,
"indexVersion": 2,
"direction": "forward",
"indexBounds": {
"ingredients .id": [
"[\"12345\", \"12345\"]"
]
},
"keysExamined": 28,
"seeks": 1,
"dupsTested": 28,
"dupsDropped": 0,
"parentName": "FETCH"
}
This seems a really straightforward situation but it is showing to be highly inefficient, any ideas how to improve?