Database
db={"cities":[{"_id":ObjectId("650fb9104b1cf1519e4c5957"),"country":"us","city":"New York"},{"_id":ObjectId("650fb9104b1cf1519e4c5958"),"country":"us","city":"Los Angeles"}]}
Query
db.cities.aggregate([{"$match":{"$expr":{"$eq":[{"$toLower":{"$replaceAll":{"input":"$city","find":" ","replacement":""}}},"newyork"]}}}])