[{_id:ObjectId("6644d9860e3b38f3dd724241"),fields:{allowed_urls:[{url:"/my_url/",method:"POST"},{url:"/my_url/",method:"GET"}]}},{_id:ObjectId("7644d9860e3b38f3dd724241"),fields:{allowed_urls:[{url:"/another_url/",method:"POST"},{url:"/my_url/",method:"GET"}]}},{_id:ObjectId("8644d9860e3b38f3dd724241"),fields:{allowed_urls:[{url:"/my_url/",method:"POST",other:"only with elemMatch"},{url:"/my_url/",method:"GET"}]}}]

db.collection.find({"fields.allowed_urls":{"method":"POST","url":"/my_url/"}})