PCDE Design and implement database schemas Practice Question
This PCDE practice question tests your understanding of design and implement database schemas. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 game company uses Cloud Bigtable to store player session data. Access patterns include looking up a player's most recent sessions and scanning sessions by time range. Which row key design is most appropriate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a row key of player ID followed by reversed timestamp.
Option B is correct because using reversed timestamp as part of the row key helps distribute writes and allows efficient range scans over recent data. Option A is wrong because timestamp first can cause hotspotting. Option C is wrong because sequential player IDs cause hotspotting on a single tablet. Option D is wrong because hashing alone makes range scans impossible.
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 only player ID as row key with column qualifiers for timestamps.
Why it's wrong here
Single row per player will be too wide and cause hotspotting on popular players.
✓
Use a row key of player ID followed by reversed timestamp.
Why this is correct
Player ID distributes writes across tablets; reversed timestamp makes recent data appear at the start of the range for efficient scans.
Related concept
Static NAT maps one inside address to one outside address.
✗
Prefix with timestamp and append player ID.
Why it's wrong here
Prefixing with timestamp causes all writes to go to the same tablet at a given time, creating hotspots.
✗
Use a hash of player ID as row key and store timestamps in cell versions.
Why it's wrong here
Hashing distributes writes but loses natural ordering, making time range scans inefficient.
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 a row key of player ID followed by reversed timestamp. — Option B is correct because using reversed timestamp as part of the row key helps distribute writes and allows efficient range scans over recent data. Option A is wrong because timestamp first can cause hotspotting. Option C is wrong because sequential player IDs cause hotspotting on a single tablet. Option D is wrong because hashing alone makes range scans impossible.
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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