How Efficient Is Google App Engine Ndb.delete_multi()?

I'm working on something to clear my database of ~10,000 entities, and my plan is to put it in a task that deletes 200 at a time using ndb.delete_multi() and then recursively calls

Solution 1:

When you delete an entity, the Datastore has to remove an entity and a record from an index for each indexed property as well as for each custom index. The number of writes is not dependent on which delete method you use.

Solution 2:

Your code example is extremely inefficient. If you are deleting large numbers of entities than you will need to batch the below but, you should be retrieving data with a keys_only query and then deleting:

from google.appengine.ext import ndb

ndb.delete_multi(
    MyModel.query().fetch(keys_only=True)
)

In regards to the number of write operations (see Andrei's answer), ensure only the fields on your model that are required to be indexed "have an index enabled".