PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A team is migrating an Oracle database to Cloud Spanner. They have a large table with an auto-increment primary key. Which key design strategy should they use to avoid hot spots?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a composite primary key with a hash prefix of the auto-increment value
Option A is correct because using a composite primary key with a hash prefix of the auto-increment value distributes writes across multiple splits in Cloud Spanner. Cloud Spanner uses range-based sharding; a monotonically increasing primary key (like an auto-increment value) would cause all new writes to land on the same split, creating a hot spot. By hashing the auto-increment value and prepending it to the primary key, you randomize the key distribution, ensuring writes are spread evenly across the table's splits.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 a composite primary key with a hash prefix of the auto-increment value
Why this is correct
Hash prefix distributes writes uniformly across splits.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use the auto-increment value as the primary key
Why it's wrong here
Sequential keys cause hot spots on the last tablet.
✗
Use interleaved tables to colocate related data
Why it's wrong here
Interleaving does not solve the hot spot issue in the primary key.
✗
Use UUID as the primary key
Why it's wrong here
UUIDs are not monotonically increasing but can still cause some hot spots; also larger size.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think UUIDs are always the best solution for avoiding hot spots in distributed databases, but in Cloud Spanner, a hash prefix of the auto-increment value is more storage-efficient and avoids the performance overhead of large primary keys, while still achieving even write distribution.
Detailed technical explanation
How to think about this question
Cloud Spanner splits data into tablets based on the primary key range; each split is served by a specific node. A hash prefix (e.g., using SHA256 or a simple modulo operation) on the auto-increment value ensures that consecutive values map to different splits, distributing write load. In practice, you might use a hash of the auto-increment value modulo the number of splits (e.g., 1000) as the first part of a composite key, then append the original auto-increment value for uniqueness. This approach also supports efficient point lookups if the hash prefix is known, though range scans become less efficient because data is scattered.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a composite primary key with a hash prefix of the auto-increment value — Option A is correct because using a composite primary key with a hash prefix of the auto-increment value distributes writes across multiple splits in Cloud Spanner. Cloud Spanner uses range-based sharding; a monotonically increasing primary key (like an auto-increment value) would cause all new writes to land on the same split, creating a hot spot. By hashing the auto-increment value and prepending it to the primary key, you randomize the key distribution, ensuring writes are spread evenly across the table's splits.
What should I do if I get this PCDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.