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PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions
A company is designing a schema for Cloud Spanner for an order management system. They need to ensure efficient joins between Order and OrderItems tables. Which TWO design practices should they adopt? (Choose 2)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use parent-child interleaving for Order and OrderItems
Parent-child interleaving places child rows physically near parent rows, enabling efficient joins. Using the OrderId as the primary key of Order and also as the first part of the primary key of OrderItems (with a line item identifier) allows for strongly consistent interleaved queries.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use parent-child interleaving for Order and OrderItems
Why this is correct
Interleaving optimizes joins between parent and child tables.
- ✗
Use a monotonically increasing primary key for Order
Why it's wrong here
Monotonically increasing keys cause hotspots in Spanner.
- ✗
Store OrderItems in a separate database
Why it's wrong here
Unnecessary; Spanner supports interleaved tables.
- ✓
Use UUID as primary key for Order
Why this is correct
UUID distributes writes evenly, avoiding hotspots.
- ✗
Denormalize OrderItems into an array column in Order
Why it's wrong here
Spanner supports array columns, but this breaks normal form and may limit query flexibility.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCDE exam.