Database
[{"_id":ObjectId("625167ce3859b8465ccf69dc"),"name":{"en":"Category #1"},"tracks":[ObjectId("627f8475c229513838eed070"),ObjectId("627f84b4c229513838eed074"),ObjectId("6280ef548b97521c1f462266"),ObjectId("6280ef68d147e83534f4ca03"),ObjectId("6280ef6ad147e83534f4ca07"),ObjectId("6280ef6bd147e83534f4ca0b"),ObjectId("6280ef68d147e83534f4ca02"),ObjectId("6280ef6ad147e83534f4ca01"),ObjectId("6280ef6bd147e83534f4ca03")]}]
Query
db.collection.aggregate([{$match:{_id:ObjectId("625167ce3859b8465ccf69dc")}},{"$addFields":{avilableCount:{$max:[{$subtract:[{$size:"$tracks"},10]},0]}}},{$project:{tracks:{$cond:[{$eq:["$avilableCount",0]},[],{$slice:["$tracks",{$max:[{$subtract:[{$size:"$tracks"},10]},0]},{$min:[2,"$avilableCount"]}]}]}}}])