- A
Increase the number of Spanner nodes to reduce the probability of deadlocks.
Why wrong: Adding nodes increases throughput but does not eliminate deadlocks; it also increases cost and may not address the root cause.
- B
Reduce the size of each transaction by splitting them into smaller ones.
Why wrong: Smaller transactions may reduce contention but require code changes and do not eliminate the need for retry logic; they may also break business logic.
- C
Change the transaction isolation level to READ UNCOMMITTED to avoid deadlocks.
Why wrong: Spanner does not support READ UNCOMMITTED; its strong consistency model requires serializable isolation, and weakening it would violate correctness.
- D
Implement retry logic with exponential backoff and random jitter for aborted transactions.
Retrying with backoff and jitter is the standard pattern for handling Spanner aborts, ensuring transient conflicts are resolved without significant latency impact.
Quick Answer
The answer is to implement retry logic with exponential backoff and random jitter for aborted transactions. This is correct because Cloud Spanner uses optimistic concurrency control, where deadlock detection is a normal, expected behavior under contention—an ABORTED error does not indicate a system fault but rather a transient conflict that can be resolved by retrying the transaction. On the Google Professional Cloud Developer exam, this scenario tests your understanding that Spanner’s distributed architecture relies on client-side retry handling, not infrastructure changes; a common trap is to suggest increasing resources or switching isolation levels, which would not fix the deadlock retry mechanism. Remember the key principle: in Spanner, ABORTED is not a failure—it’s an invitation to retry. Memory tip: think “ABORTED = Always Back Off, Retry with Timed Exponential Delay.”
PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. 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 financial services company runs a transaction processing microservice on Google Kubernetes Engine (GKE). The service uses Cloud Spanner as its database. After migrating from Cloud SQL to Spanner to improve scalability, the team notices that a small percentage of transactions fail with an 'ABORTED' error due to deadlock detection. The application currently performs no retries, and the failures cause customer-facing errors. The team also observes that under peak load, transaction latencies are around 500ms, which is acceptable but they want to ensure the system remains reliable. They need to implement a solution that minimizes failures while maintaining acceptable performance. Which course of action should they take?
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
Implement retry logic with exponential backoff and random jitter for aborted transactions.
In Cloud Spanner, 'ABORTED' errors due to deadlock detection are a normal part of the optimistic concurrency control mechanism. The correct solution is to implement retry logic with exponential backoff and random jitter, as recommended by Google's own documentation. This approach transparently handles transient deadlocks without requiring infrastructure changes or sacrificing consistency, and it maintains acceptable latency by spacing out retries.
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.
- ✗
Increase the number of Spanner nodes to reduce the probability of deadlocks.
Why it's wrong here
Adding nodes increases throughput but does not eliminate deadlocks; it also increases cost and may not address the root cause.
- ✗
Reduce the size of each transaction by splitting them into smaller ones.
Why it's wrong here
Smaller transactions may reduce contention but require code changes and do not eliminate the need for retry logic; they may also break business logic.
- ✗
Change the transaction isolation level to READ UNCOMMITTED to avoid deadlocks.
Why it's wrong here
Spanner does not support READ UNCOMMITTED; its strong consistency model requires serializable isolation, and weakening it would violate correctness.
- ✓
Implement retry logic with exponential backoff and random jitter for aborted transactions.
Why this is correct
Retrying with backoff and jitter is the standard pattern for handling Spanner aborts, ensuring transient conflicts are resolved without significant latency impact.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that scaling infrastructure (more nodes) or reducing transaction size alone can eliminate deadlocks, when in fact retry logic is the required pattern for handling transient aborts in distributed databases like Cloud Spanner.
Detailed technical explanation
How to think about this question
Cloud Spanner uses pessimistic locking combined with optimistic concurrency control; when a deadlock is detected, one transaction is chosen as the victim and aborted with an 'ABORTED' error. The recommended retry pattern uses exponential backoff (e.g., starting at 10ms and doubling up to a maximum) with random jitter to avoid thundering herd problems. This is a standard pattern for distributed databases like Spanner and is also used in Google's own client libraries.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCD question test?
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Implement retry logic with exponential backoff and random jitter for aborted transactions. — In Cloud Spanner, 'ABORTED' errors due to deadlock detection are a normal part of the optimistic concurrency control mechanism. The correct solution is to implement retry logic with exponential backoff and random jitter, as recommended by Google's own documentation. This approach transparently handles transient deadlocks without requiring infrastructure changes or sacrificing consistency, and it maintains acceptable latency by spacing out retries.
What should I do if I get this PCD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 25, 2026
This PCD 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 PCD exam.
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