- A
Partition the data by date and store in separate directories for each partition.
Why wrong: While partitioning can improve query performance, it doesn't reduce storage cost; also BigLake supports partition pruning with Hive partitioning but that's not a direct cost-saving action.
- B
Configure object lifecycle management to transition files older than 90 days to Nearline storage.
Lifecycle policies automatically move data to cheaper storage classes, reducing cost.
- C
Convert all JSON files to CSV to reduce storage size.
Why wrong: CSV may be larger for nested data; JSON is fine and BigQuery supports it. Conversion adds overhead.
- D
Use BigLake to create external tables with row-level security and access delegation.
BigLake provides unified access control and enables querying Cloud Storage data directly with BigQuery.
- E
Enable Cloud KMS to encrypt the data with customer-managed encryption keys.
Why wrong: While KMS adds security, it does not directly reduce storage costs; data is already encrypted at rest.
Quick Answer
The correct actions are to use BigLake to create external tables with row-level security and access delegation, and to implement object lifecycle management to move older data to colder storage classes. BigLake bridges Cloud Storage and BigQuery by allowing direct querying of external data while enforcing fine-grained security controls like row-level filtering, which is essential for protecting sensitive patient records in a healthcare data lake. Object lifecycle management reduces costs by automatically transitioning infrequently accessed JSON files from Standard to Nearline or Coldline storage without sacrificing queryability. On the Google Professional Data Engineer exam, this question tests your understanding of how to balance security and cost optimization in a data lake architecture—a common scenario where candidates mistakenly choose encryption options or partitioning, which do not directly address cost. Remember the mnemonic “BigLake for security, Lifecycle for savings” to keep the two distinct actions straight.
PDE Designing data processing systems Practice Question
This PDE practice question tests your understanding of designing data processing systems. 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 healthcare company stores patient records as JSON files in Cloud Storage for analysis. They want to design a data lake that enables querying the data with BigQuery while minimizing storage costs and maintaining data security. Which two actions should they take? (Choose two.)
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
Configure object lifecycle management to transition files older than 90 days to Nearline storage.
Correct answers are A and C. Option A is correct because BigLake allows BigQuery to query Cloud Storage data with fine-grained access control and supports various formats. Option C is correct because object lifecycle management can move old data to colder storage classes (e.g., Nearline, Coldline) to reduce costs. Option B is incorrect because encryption is already default; Cloud KMS provides additional control but is not a cost-saving measure. Option D is incorrect because CSV is less efficient for nested data; JSON or Parquet is better. Option E is incorrect because partitioning in BigQuery is for managed tables, not for external tables on Cloud Storage (BigLake supports partitioning but not automatic; however, it's not the primary cost or security action).
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.
- ✗
Partition the data by date and store in separate directories for each partition.
Why it's wrong here
While partitioning can improve query performance, it doesn't reduce storage cost; also BigLake supports partition pruning with Hive partitioning but that's not a direct cost-saving action.
- ✓
Configure object lifecycle management to transition files older than 90 days to Nearline storage.
Why this is correct
Lifecycle policies automatically move data to cheaper storage classes, reducing cost.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Convert all JSON files to CSV to reduce storage size.
Why it's wrong here
CSV may be larger for nested data; JSON is fine and BigQuery supports it. Conversion adds overhead.
- ✓
Use BigLake to create external tables with row-level security and access delegation.
Why this is correct
BigLake provides unified access control and enables querying Cloud Storage data directly with BigQuery.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Enable Cloud KMS to encrypt the data with customer-managed encryption keys.
Why it's wrong here
While KMS adds security, it does not directly reduce storage costs; data is already encrypted at rest.
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 PDE NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this PDE question test?
Designing data processing systems — This question tests Designing data processing systems — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Configure object lifecycle management to transition files older than 90 days to Nearline storage. — Correct answers are A and C. Option A is correct because BigLake allows BigQuery to query Cloud Storage data with fine-grained access control and supports various formats. Option C is correct because object lifecycle management can move old data to colder storage classes (e.g., Nearline, Coldline) to reduce costs. Option B is incorrect because encryption is already default; Cloud KMS provides additional control but is not a cost-saving measure. Option D is incorrect because CSV is less efficient for nested data; JSON or Parquet is better. Option E is incorrect because partitioning in BigQuery is for managed tables, not for external tables on Cloud Storage (BigLake supports partitioning but not automatic; however, it's not the primary cost or security action).
What should I do if I get this PDE 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 PDE 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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Last reviewed: Jun 24, 2026
This PDE 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 PDE exam.
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