text: use('contactsData')
  
  // Some tools (methods) that help us to analyze the result
  // explain()
  db.contacts.explain().find({ 'dob.age': { $gt: 60 } });
  // explain('executionStats')
  db.contacts.explain('executionStats').find({ 'dob.age': { $gt: 60 } });
  // explain('queryPlanner'), explain('allPlansExecution')
  
  // Create an Index
  // Ascending
  db.contacts.createIndex({ 'dob.age': 1 });
  // Descending
  db.contacts.createIndex({ 'dob.age': -1 });