- A
Create the index using ALTER TABLE with 'ONLINE' clause
Why wrong: The correct syntax is CREATE INDEX; ALTER TABLE is for schema changes but not for index creation.
- B
Use gcloud spanner databases ddl update with --async flag
Why wrong: The async flag does not avoid blocking; schema changes like CREATE INDEX are already non-blocking.
- C
Take a backup, create index on a new instance, and switch traffic
Why wrong: This is cumbersome and unnecessary; Spanner supports online index creation.
- D
Use CREATE INDEX; Spanner handles it as a non-blocking operation
Spanner perform index creation as a background operation that does not block writes.
Question 180 of 1,000
PCDOE Manage Database Solutions Practice Question
This PCDOE practice question tests your understanding of manage database solutions. 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 company uses Cloud Spanner for a global inventory application. They need to add a new index to a large table without downtime. What is the recommended approach?
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 CREATE INDEX; Spanner handles it as a non-blocking operation
Option D is correct because Cloud Spanner's CREATE INDEX operation is inherently non-blocking; it performs the index backfill as a background process without locking the table or blocking reads and writes. This allows the index to be added to a large table with zero downtime, as Spanner manages the consistency and availability of the data throughout the operation.
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.
- ✗
Create the index using ALTER TABLE with 'ONLINE' clause
Why it's wrong here
The correct syntax is CREATE INDEX; ALTER TABLE is for schema changes but not for index creation.
- ✗
Use gcloud spanner databases ddl update with --async flag
Why it's wrong here
The async flag does not avoid blocking; schema changes like CREATE INDEX are already non-blocking.
- ✗
Take a backup, create index on a new instance, and switch traffic
Why it's wrong here
This is cumbersome and unnecessary; Spanner supports online index creation.
- ✓
Use CREATE INDEX; Spanner handles it as a non-blocking operation
Why this is correct
Spanner perform index creation as a background operation that does not block writes.
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 Cloud Spanner requires special syntax or flags (like ONLINE or --async) to achieve non-blocking DDL, when in fact all DDL operations in Spanner are designed to be non-blocking by default.
Detailed technical explanation
How to think about this question
Under the hood, Cloud Spanner implements index creation using a distributed, asynchronous backfill process that reads the base table in parallel across splits, applies the index entries, and uses commit timestamps to ensure transactional consistency without blocking concurrent DML. A subtle behavior is that while the index is being built, it is not yet available for queries, but the base table remains fully accessible; once the backfill completes, the index becomes active atomically. In a real-world scenario, a global inventory application with terabytes of data can add a new index without any application changes or maintenance windows, relying on Spanner's horizontal scaling to complete the backfill in a predictable timeframe.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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.
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Manage Database Solutions — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this PCDOE question test?
Manage Database Solutions — This question tests Manage Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use CREATE INDEX; Spanner handles it as a non-blocking operation — Option D is correct because Cloud Spanner's CREATE INDEX operation is inherently non-blocking; it performs the index backfill as a background process without locking the table or blocking reads and writes. This allows the index to be added to a large table with zero downtime, as Spanner manages the consistency and availability of the data throughout the operation.
What should I do if I get this PCDOE 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.
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Last reviewed: Jul 4, 2026
This PCDOE 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 PCDOE exam.
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