query do
    where(activated: true).consistency(:strong)
    # or
    where(activated: true).consistency(:eventual)
end

SubscriptionRepository.find('8565').id # => nil

# mapping
collection :subscriptions do
  entity     Subscription
  repository SubscriptionRepository

  attribute :id,       Integer, as: :Id
  attribute :schedule, String,  as: :Schedule
end

SubscriptionRepository.find('8565')
s # => #<Subscription:0x0055692cda4950 @id=nil @schedule=nil>

user_key = Gcloud::Datastore::Key.new "User", "alice"
task_list_key = Gcloud::Datastore::Key.new "TaskList", "default"
task_key = Gcloud::Datastore::Key.new "Task", "sampleTask"
task_list_key.parent = user_key
task_key.parent = task_list_key
dataset.find task_key

user_key = ['User', 'alice']
task_list_key = ['TaskList', 'default', { parent: user_key }]
task_key = ['Task', 'sampleTask', { parent: task_list_key }]
task = Task.new(id: task_key)
TaskRepository.persist(task)

# first
query = dataset.query('Subscription').order('__key__', :asc).limit(1)
dataset.run(query).first

# last
query = dataset.query('Subscription').order('__key__', :desc).limit(1)
dataset.run(query).first