db={"users":[{"_id":ObjectId("5ff0c73e5930dd43c05ac221"),"userRefID":"07f426ff-506f-4e5e-afdb-2c7397edac61","userName":"EPS Purecloud Support","divisionId":"36852a81-ad7f-4c71-a1cd-7f431c05179f","divisionName":"","emailId":"eps@genesys.com","__v":0},{"_id":ObjectId("5ff0c73e5930dd43c05ac222"),"userRefID":"c5ce06dc-6265-4d16-be18-f5fc5a918295","userName":"Generic","divisionId":"36852a81-ad7f-4c71-a1cd-7f431c05179f","divisionName":"","emailId":"integration-generic-a03293c0-945d-11ea-a64c-ebeb45b9d295@webhook.com","__v":0}],"roles":[{"_id":ObjectId("5ff0fb02b21b1d0760f3107b"),"userRefID":"07f426ff-506f-4e5e-afdb-2c7397edac61","skillRefId":"c02dbb03-ed78-442a-a9cd-0f16c823646b","queueName":"CIM_test","__v":0},{"_id":ObjectId("5ff0fb02b21b1d0760f3107c"),"userRefID":"07f426ff-506f-4e5e-afdb-2c7397edac61","skillRefId":"a626d99e-f5e9-47ab-a5d0-d493003c737f","queueName":"CLAIMS","__v":0},{"_id":ObjectId("5ff0fb02b21b1d0760f3107d"),"userRefID":"07f426ff-506f-4e5e-afdb-2c7397edac61","skillRefId":"9b31524c-b574-4917-b470-8b86f430beaa","queueName":"CSS_AZ_IND_BILL_EN_1","__v":0},{"_id":ObjectId("5ff0fb03b21b1d0760f310b3"),"userRefID":"c5ce06dc-6265-4d16-be18-f5fc5a918295","skillRefId":"f3bf0897-1b63-4a03-9f8f-5b18fc03401b","queueName":"Aflac","__v":0},{"_id":ObjectId("5ff0fb03b21b1d0760f310b4"),"userRefID":"c5ce06dc-6265-4d16-be18-f5fc5a918295","skillRefId":"c02dbb03-ed78-442a-a9cd-0f16c823646b","queueName":"CIM_test","__v":0}]}

db.users.aggregate([{"$lookup":{"from":"roles","let":{"users_userrefid":"$userRefID"},"pipeline":[{$match:{"$expr":{"$eq":["$userRefID","$$users_userrefid"]}}},{"$project":{__v:0,_id:0}}],"as":"roles"}}])