The answer is to use secondary indexes and interleaved tables. Secondary indexes improve point-read performance by allowing Cloud Spanner to serve individual row lookups directly from the index table, bypassing the need for a full table scan and significantly reducing latency. Interleaved tables, meanwhile, store child rows physically adjacent to their parent row on the same split, enabling efficient single-row lookups without costly cross-node coordination. On the Google Professional Cloud Developer exam, this question tests your understanding of Spanner’s distributed storage architecture and how to optimize for low-latency reads in a global application. A common trap is to assume that adding more indexes always helps, but secondary indexes add write overhead, while interleaved tables are ideal for hierarchical data with strong parent-child relationships. Remember the memory tip: “Index for direct hits, interleave for family ties.”
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 company uses Cloud Spanner for a global application. They want to improve read performance for point-reads (individual row lookups). Which TWO strategies should they adopt?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create secondary indexes
Secondary indexes in Cloud Spanner allow point-reads to be served directly from the index table, avoiding a full table scan and reducing latency. Interleaved tables store child rows physically adjacent to their parent row, enabling efficient single-row lookups without cross-node coordination.
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 read replicas
Why it's wrong here
Spanner does not have read replicas; all replicas are writable.
✓
Create secondary indexes
Why this is correct
Secondary indexes enable efficient point reads on columns other than the primary key.
Related concept
Read the scenario before looking for a memorised answer.
✗
Partition the table by time
Why it's wrong here
Time-based partitioning helps with time-range queries, not point reads.
✗
Use batch reads
Why it's wrong here
Batch reads are for retrieving multiple rows, not optimizing individual point reads.
✓
Use interleaved tables
Why this is correct
Rows in interleaved tables are physically colocated, speeding up point reads.
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 read replicas or batch operations improve point-read latency, when in fact they address throughput or bulk retrieval, not the speed of individual row lookups.
Detailed technical explanation
How to think about this question
Cloud Spanner uses a distributed, Paxos-based storage architecture where each row is stored in a specific split. Secondary indexes are stored as separate tables that map indexed column values to the primary key, allowing point-reads to be resolved by a single split lookup. Interleaved tables leverage the parent-child relationship to co-locate rows in the same split, eliminating cross-split round trips for hierarchical data access.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Create secondary indexes — Secondary indexes in Cloud Spanner allow point-reads to be served directly from the index table, avoiding a full table scan and reducing latency. Interleaved tables store child rows physically adjacent to their parent row, enabling efficient single-row lookups without cross-node coordination.
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.
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Question Discussion
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