You are developing an application that will allow users to read and post comments on news articles. You want to configure your application to store and display user-submitted comments using Firestore.

Question

Options

• AStore each comment in a subcollection of the article.
• BAdd each comment to an array property on the article.
• CStore each comment in a document, and add the comment's key to an array property on the
• DStore each comment in a document, and add the comment's key to an array property on the user

• A
  73% (22)
• B
  3% (1)
• C
  13% (4)
• D
  10% (3)

Explanation

Firestore subcollections are the idiomatic way to model one-to-many relationships with an unbounded number of child documents. Storing each comment as a document in a subcollection under its parent article document (e.g., /articles/{articleId}/comments/{commentId}) allows unlimited comments per article, efficient querying, and scalable reads. Option B (array on the article document) is problematic because Firestore document size is capped at 1 MB and arrays cannot be queried or paginated efficiently. Options C and D (storing comment keys in arrays) still inherit the array size and document size limitations while adding unnecessary indirection.

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