[{"time":1422471890,"user_id":"256f5280-fb49-4ad6-b7f5-65c4329d46e0","message":"This is an example of my db"},{"time":1622471890,"user_id":"256f5280-fb49-4ad6-b7f5-65c4329d46e0","message":"This is an example of my db (1)"},{"time":1622471890,"user_id":"256f5280-fb49-4ad6-b7f5-65c4329d46e0","message":"This is an example of my db (2)"},{"time":1622471890,"user_id":"e194d667-d79f-4262-94b1-ecf4561c9418","message":"This is an example of my db (3)"},{"time":1922471890,"user_id":"256f5280-fb49-4ad6-b7f5-65c4329d46e0","message":"This is an example of my db (4)"}]

db.collection.aggregate([{$match:{$and:[{user_id:"256f5280-fb49-4ad6-b7f5-65c4329d46e0"},{time:{$gte:1622471890,$lt:1822471890}}]}},{"$count":"value"},{"$addFields":{"value":{"$cond":{"if":{"$gt":["$value",0]},"then":"$value","else":0}}}},{"$unionWith":{"coll":"collection","pipeline":[{$limit:1}]}},{"$sort":{value:-1}},{$limit:1},{"$project":{_id:0,value:{"$ifNull":["$value",0]}}}])