The correct choice is to modify the primary key to include a hash of the original key as a leading column. This approach directly addresses Cloud Spanner hotspotting prevention with hash prefix by distributing writes across multiple splits, preventing the monotonically increasing key from concentrating all new inserts on a single node. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of how Cloud Spanner’s split-based architecture handles write throughput; a common trap is to assume that adding an index or changing the key order alone will solve the bottleneck, but only a leading hash prefix spreads the load uniformly. Remember the memory tip: “Hash the head to spread the lead”—by hashing the leading column, you break the sequential pattern and eliminate the hotspot.
PCDE Design and implement database schemas Practice Question
This PCDE practice question tests your understanding of design and implement database schemas. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 Cloud Spanner application experiences high write latency on a table with a monotonically increasing primary key. Which schema change will most effectively reduce latency?
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
✓
Modify the primary key to include a hash of the original key as a leading column
Option B is correct: adding a hash prefix to the primary key spreads writes across nodes, eliminating hotspotting. Option A is the current problem. Options C and D do not directly address the underlying hotspotting issue.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Convert the table to an interleaved table
Why it's wrong here
Interleaving does not fix hotspotting from the parent key.
✗
Add a secondary index on the existing key
Why it's wrong here
Indexes do not alleviate primary key hotspotting.
✓
Modify the primary key to include a hash of the original key as a leading column
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
Static NAT maps one inside address to one outside address.
✗
Increase the number of nodes in the instance
Why it's wrong here
Scaling nodes helps throughput but does not resolve single-key hotspotting.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCDE NAT questions on configuration and troubleshooting.
Design and implement database schemas — This question tests Design and implement database schemas — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Modify the primary key to include a hash of the original key as a leading column — Option B is correct: adding a hash prefix to the primary key spreads writes across nodes, eliminating hotspotting. Option A is the current problem. Options C and D do not directly address the underlying hotspotting issue.
What should I do if I get this PCDE question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCDE NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO techniques can help avoid hot spotting in a Cloud Spanner table?
hard
✓ A.Add a hash of the primary key as the first part of the key
B.Use a monotonically increasing integer as the key
C.Use interleaved tables to distribute writes
D.Create a secondary index on a high-cardinality column
✓ E.Use a random prefix or UUID as the first key column
Why A: Option A is correct: hash prefix distributes writes across splits. Option B is correct: using a random prefix also spreads writes, though hash prefix is more common. Option C is incorrect: monotonically increasing keys cause hotspotting. Option D is incorrect: interleaving does not prevent hotspotting on the parent key. Option E is incorrect: secondary indexes can cause their own hotspotting.
Last reviewed: Jun 24, 2026
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.
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.