Exercise 3: Migrating From Cloud Datastore Without Rewriting Code — Possible Solution
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Firestore's real Datastore mode exists specifically for this
situation - it was built as a compatibility mode for applications
already written against the older Cloud Datastore service, using the
same real entity-based data model Cloud Datastore used, so existing
data-access code can keep working largely unchanged.

Native mode, by contrast, is the modern, recommended choice for new
projects - it uses Firestore's own document/collection model and adds
real-time sync and offline support, but it is not the compatibility
path this team needs. Both modes share the same real underlying
infrastructure, so choosing Datastore mode does not mean giving up
Firestore's own managed, serverless platform - it just keeps the data
model the existing code already expects.

ANSWER: The team should use Firestore's Datastore mode, which was
built specifically for this scenario - it preserves Cloud Datastore's
own entity-based data model so existing data-access code continues to
work without a rewrite, while still running on Firestore's own
managed infrastructure.

WHY THIS WORKS AS AN ANSWER
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This correctly identifies Datastore mode as the real, purpose-built
compatibility path described in the chapter, and explains why it
avoids the code rewrite the team wants to avoid, distinguishing it
from Native mode's own different, non-compatible data model.