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Data Consistency in Datastore Queries
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Data consistency levels
Datastore queries can deliver their results at either of two consistency
levels:
In an eventually consistent query, the indexes used to gather the results are also accessed with eventual consistency. Consequently, such queries may sometimes return entities that no longer match the original query criteria, while strongly consistent queries are always transactionally consistent.
Datastore query data consistency
Queries return their results with different levels of consistency guarantee, depending on the nature of the query:
- Ancestor queries (those within an
entity group
)
are strongly consistent by default, but can instead be made eventually
consistent by setting the Datastore read policy (see below).
- Non-ancestor queries are always eventually consistent.
Fetching an entity by key, which is also called "lookup by key", is strongly
consistent.
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Last updated 2025-08-07 UTC.
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