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.
A data warehouse in BigQuery stores event logs with nested and repeated fields (e.g., page views within a session). Which schema type is optimal for storing this data?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use ARRAY<STRUCT<...>> columns for nested repeated data
Option D is correct: ARRAY<STRUCT<...>> allows storing nested repeated data natively in BigQuery, enabling efficient querying without joins. Option A (separate tables) requires costly joins. Option B (JSON strings) loses schema enforcement and performance. Option C (RECORD type) is a legacy term; the current best practice is arrays of structs.
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.
✗
Use RECORD type columns for each nested level
Why it's wrong here
RECORD type is a single struct; repeated fields require ARRAY<STRUCT>.
✗
Normalize into separate tables and join
Why it's wrong here
Joins are expensive in BigQuery; nested repeated fields are preferred.
✓
Use ARRAY<STRUCT<...>> columns for nested repeated data
Why this is correct
Arrays of structs are the native way to represent nested repeated data in BigQuery.
Related concept
Static NAT maps one inside address to one outside address.
✗
Store as JSON strings and parse at query time
Why it's wrong here
JSON requires manual parsing and lacks schema enforcement.
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: Use ARRAY<STRUCT<...>> columns for nested repeated data — Option D is correct: ARRAY<STRUCT<...>> allows storing nested repeated data natively in BigQuery, enabling efficient querying without joins. Option A (separate tables) requires costly joins. Option B (JSON strings) loses schema enforcement and performance. Option C (RECORD type) is a legacy term; the current best practice is arrays of structs.
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.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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