db={"teams":[{"_id":"t1","name":"white horse","leader_id":"L1","teamScore":12,"active":1},{"_id":"t2","name":"green hornets","leader_id":"L2","teamScore":9,"active":1},{"_id":"t3","name":"pink flaminggo","leader_id":"L3","teamScore":22,"active":1}],"leaders":[{"_id":"L1","name":"John Doe","organization":"Software Development","active":1},{"_id":"L2","name":"Peter Piper","organization":"Software Development","active":1},{"_id":"L3","name":"Mary Lamb","organization":"Accounting Department","active":1}]}

db.teams.aggregate([{$match:{active:1}},{$lookup:{from:"leaders",let:{leader_id:"$leader_id"},as:"leaders",pipeline:[{$match:{$and:[{$expr:{$eq:["$_id","$$leader_id"]}},{"organization":"Software Development"}]}}]}},{$match:{leaders:{$ne:[]}}},{$project:{leaders:0}}])