You are a developer at a social media company. The company runs their social media website on-premises and uses MySQL as a backend to store user profiles and user posts. Your company plans to…

Question

Options

• ACreate one root collection for user profiles, and create one root collection for user posts.
• BCreate one root collection for user profiles, and create one subcollection for each user's posts.
• CCreate one root collection for user profiles, and store each user's post as a nested list in the user
• DCreate one root collection for user posts, and create one subcollection for each user's profile.

• A
  7% (2)
• B
  83% (25)
• C
  7% (2)
• D
  3% (1)

Explanation

In Firestore, subcollections are the idiomatic way to model one-to-many relationships. Creating one root collection for user profiles and a subcollection per user for their posts allows efficient queries like 'get all posts for user X' without scanning the entire post dataset. Option A (two root collections) works but requires client-side joins or denormalization and is less idiomatic. Option C (nested list inside the user document) is dangerous because Firestore documents have a hard 1 MB size limit - a user with many posts would exceed this. Option D inverts the hierarchy in a way that makes fetching a user's profile alongside their posts unnecessarily complex.

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