Find mongodb docs based on array of object contains two fields

simple $or

db.collection.aggregate([
  {
    "$match": {
      "$or": [
        {
          "user_id": 1,
          "lead_id": 901
        },
        {
          "user_id": 2,
          "lead_id": 902
        }
      ]
    }
  }
])

mongoplayground

node

const reqArr = [
  {
    "user_id": 1,
    "lead_id": 901,
  }, 
   {
    "user_id": 2,
    "lead_id": 999,
   }
]
Model.find({ "$or": reqArr})

The simplest way to do the above would be this:

const results = await Promise.all(reqArr.map(req => {
    const { user_id, lead_id } = req;
    return Model.findOne({ user_id, lead_id });
}));

We map over each item in reqArr. For each item (req), we destructure into two variables user_id and lead_id.

We then query for a single document (I assume there is only one document for each user_id and lead_id pair, otherwise this will need to be slightly adjusted.

We then return the findOne promise, resulting in an array of promises which we pass into Promise.all to await them all asynchronously.

This should result flat array of results that match the lead_iq/user_id pairs in reqArr.

If some of these combos aren't present in the database, those elements of the array will be undefined and you can go on to handle those however you need to.