The answer is that secondary indexes can be created with a STORING clause to include non-key columns, they are strongly consistent with the base table, and they can be created on child tables without including the parent key. These three considerations are valid because Cloud Spanner secondary indexes are designed to provide global, strongly consistent lookups without requiring the parent key from an interleaved hierarchy, and the STORING clause allows you to embed additional columns to avoid a back-join to the base table. On the Google Professional Cloud Database Engineer exam, this question tests your understanding of how secondary indexes differ from primary and interleaved indexes, with a common trap being the assumption that secondary indexes are automatically used for primary key filtering or that they must be unique. A useful memory tip is "STORING stores, not unique" — remember that STORING adds non-key columns for covering queries, and uniqueness is optional, not required.
PCDE Design and implement database schemas Practice Question
This PCDE practice question tests your understanding of design and implement database schemas. 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.
Which three of the following are valid considerations when designing secondary indexes in Cloud Spanner? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Secondary indexes maintain strong consistency with the base table
Options A, D, and E are correct. A is true: secondary indexes can be created on interleaved tables (but note they are not interleaved themselves). D is true: secondary indexes in Spanner are strongly consistent with the base table. E is true: secondary indexes can be created on child tables without including the parent key, though they are not interleaved. B is false because secondary indexes are not automatically used for primary key filtering; the primary index is used. C is false because secondary indexes do not require a unique constraint; they can be non-unique.
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.
✓
Secondary indexes maintain strong consistency with the base table
Why this is correct
All indexes in Spanner are strongly consistent.
Related concept
Read the scenario before looking for a memorised answer.
✗
Secondary indexes are automatically used for queries that filter on primary key columns
Why it's wrong here
Primary key queries use the primary index; secondary indexes are not automatically used for PK filters.
✗
Secondary indexes require a unique constraint
Why it's wrong here
Secondary indexes can be non-unique; unique constraint is optional.
✓
Secondary indexes can be created on child tables without including the parent key
Why this is correct
They are still valid secondary indexes, though not interleaved.
Related concept
Read the scenario before looking for a memorised answer.
✓
Secondary indexes can be created with a STORING clause to include non-key columns
Why this is correct
Correct; STORING clause stores additional columns in the index for covering queries.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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.
Identify which PCDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Design and implement database schemas — This question tests Design and implement database schemas — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Secondary indexes maintain strong consistency with the base table — Options A, D, and E are correct. A is true: secondary indexes can be created on interleaved tables (but note they are not interleaved themselves). D is true: secondary indexes in Spanner are strongly consistent with the base table. E is true: secondary indexes can be created on child tables without including the parent key, though they are not interleaved. B is false because secondary indexes are not automatically used for primary key filtering; the primary index is used. C is false because secondary indexes do not require a unique constraint; they can be non-unique.
What should I do if I get this PCDE question wrong?
Identify which PCDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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