Database
db={"projects":[{"name":"Project 1","skillsetCombinations":[["A","B","D"],["A","B","E"],["A","C","D"]]},{"name":"Project 2","skillsetCombinations":[["X","Y","Z"],["A","B","D","E"],["U","V","W"]]},{"name":"Project 3","skillsetCombinations":[["A","B","E"],["A","C","D"],["A","B"]]}]}
Query
db.projects.find({skillsetCombinations:{$elemMatch:{$elemMatch:{$in:["A","B","D"]}}}})