I am trying to perform an update on a document in a Mongo collection. The query used to find and update a record is as below and works fine.

StringBuilder queryBuilder = new StringBuilder()
                    .append("{"date": ")
                    .append(startOfDayEpoch)
                    .append(", "key": "")
                    .append(key)
                    .append("", "appId": "")
                    .append(appId)
                    .append("", "assetId": "")
                    .append(assetId)
                    .append(""")
                    .append("}");

Update increment = processRequestCount ? Update.fromDocument(Document.parse("{"$inc": {"usedHits": "
                  + withCalculatedHits + ", "requestCount": 1}}")) :
                    Update.fromDocument(Document.parse("{"$inc": {"usedHits": " + withCalculatedHits + "}}"));
                    
UpdateResult result = mongoTemplate.updateFirst(matchClause, increment, proxyCollection);

if (result.getMatchedCount() > 0)
    return true;

Problem :

I now tried to update two more fields witht the above clause as per below

1. First is to add a condition clause in the above for a scenario like
   if usedHits > freeHits => update -> costCalculated = (freeHits-usedHits) * multiplier

2. maintain a statusCode object which increments with every request with a specific status code. For eg statusCode : 200=10, 400=3, 503=1
   When a request comes and is responded with a status code lets say 400, it should update the statusCode.400 value by 1

I tired modifying the increment Update clause using online references as below when adding the condition clause but it didn’t work with the below error

Document documentToUpdate = new Document("$set", new Document("costCalculated", new Document("$cond",
        Arrays.asList(new Document("$gte", Arrays.asList("$usedHits", freeHits)),
                new Document("$mul", Arrays.asList(new Document("$subtract", Arrays.asList("$usedHits", freeHits)), multiplier)),
                0))));
documentToUpdate.append("$inc", new Document("statusCodes."+statusCode, 1));

Update increment = Update.fromDocument(documentToUpdate);

Error : org.springframework.dao.DataIntegrityViolationException: The dollar ($) prefixed field '$cond' in 'costCalculated.$cond' is not valid for storage.; nested exception is com.mongodb.MongoWriteException: The dollar ($) prefixed field '$cond' in 'costCalculated.$cond' is not valid for storage.;

Note: I am trying to avoid pulling object first and perform the changes and write back to db but just issue an update

Also, the final document would look like

{
  "date": 1712341800,
  "expiresAfter": 1714413600,
  "key": "my_dev_key",
  "appId": "my_app_id",
  "assetName": "Sample API",
  "assetId": "asset_id",
  "usedHits": 11,
  "statusCodes": {
    "404": 1,
    "200": 11
  },
  "costCalculated": 2.2,
  "requestCount": 12
}

Could anyone please guide and point what is wrong or suggest an approach for this?