2 Answers
Hope this website will clarify it a bit more for you:
See the following differences, it might help you.
Bigtable is best for:
Petabyte-scale databases, with low latency, high read and write
store tables that can have a large number of columns.
If you are writing data at high rates and in large volumes, consider Bigtable
Datastore is best for:
Where consistency is required
for semi-structured application data that is used in app engines’ applications
Datastore is a schemaless database and does not support relational operations
is used for nonanalytic, nonrelational storage
support for transactions and indexes to improve query performance
it lets you do SQL-like queries
Great link Lewis.
Thanks but still it does not answer the overlap for me. If a client wants to use non relational storage that can handle that can handle a large volume of data. What to select ?