PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. 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 is migrating an on-premises Oracle database to Cloud SQL for PostgreSQL. The database is 2 TB in size and the network bandwidth to Google Cloud is limited to 500 Mbps. The migration window is 48 hours. Which migration strategy should the Database Engineer recommend?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Export the database to flat files, compress, upload to Cloud Storage, then import to Cloud SQL.
Option C is correct because the 2 TB database size and 500 Mbps bandwidth yield a theoretical transfer time of approximately 9.5 hours (2 TB * 1024 GB/TB * 8 bits/byte / 500 Mbps / 3600 seconds/hour), which fits within the 48-hour window. However, pg_dump/pg_restore over a VPN (Option A) would be slower due to TCP overhead and latency, and Database Migration Service with continuous replication (Option B) requires ongoing connectivity and may not complete the initial load within the window. Exporting to flat files, compressing them (e.g., with gzip), uploading to Cloud Storage, and then importing to Cloud SQL leverages high-throughput parallel uploads and avoids network latency issues, making it the most reliable strategy for a one-time migration within the given constraints.
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 a VPN tunnel and use pg_dump/pg_restore over the network.
Why it's wrong here
pg_dump over VPN is slower and less reliable than file-based migration.
✗
Use Database Migration Service with continuous replication.
Why it's wrong here
Continuous replication requires higher bandwidth and may not complete within 48 hours.
✓
Export the database to flat files, compress, upload to Cloud Storage, then import to Cloud SQL.
Why this is correct
File-based migration with compression can work within the bandwidth and time constraints.
Related concept
Read the scenario before looking for a memorised answer.
✗
Request a dedicated interconnect and then migrate.
Why it's wrong here
Setting up interconnect takes weeks, exceeding the migration window.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume Database Migration Service (Option B) is always the best choice for any migration, but they overlook that continuous replication is unnecessary for a one-time migration and that the initial load still faces the same bandwidth bottleneck as other network-based methods.
Detailed technical explanation
How to think about this question
When migrating large databases over limited bandwidth, compression is critical: flat-file exports (e.g., using pg_dump with custom format or directory format) can be compressed with gzip or bzip2, reducing the data size by 3-5x for typical relational data. Uploading to Cloud Storage uses HTTPS with multiple parallel TCP connections (e.g., via gsutil with -o GSUtil:parallel_composite_upload_threshold=150M), which can saturate the available bandwidth more efficiently than a single pg_dump stream. The import to Cloud SQL can then be done using the gcloud sql import command, which reads directly from Cloud Storage and leverages the database's internal parallelism.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Export the database to flat files, compress, upload to Cloud Storage, then import to Cloud SQL. — Option C is correct because the 2 TB database size and 500 Mbps bandwidth yield a theoretical transfer time of approximately 9.5 hours (2 TB * 1024 GB/TB * 8 bits/byte / 500 Mbps / 3600 seconds/hour), which fits within the 48-hour window. However, pg_dump/pg_restore over a VPN (Option A) would be slower due to TCP overhead and latency, and Database Migration Service with continuous replication (Option B) requires ongoing connectivity and may not complete the initial load within the window. Exporting to flat files, compressing them (e.g., with gzip), uploading to Cloud Storage, and then importing to Cloud SQL leverages high-throughput parallel uploads and avoids network latency issues, making it the most reliable strategy for a one-time migration within the given constraints.
What should I do if I get this PCDE 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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