DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 gaming company uses Amazon DynamoDB to store player scores. The table has a partition key of 'game_id' and a sort key of 'player_id'. The application needs to retrieve the top 10 players for a given game_id based on score (stored as an attribute). The game_id has high cardinality. The team wants to avoid full table scans. Which design pattern is MOST efficient?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a global secondary index with partition key game_id and sort key score
DynamoDB does not support ORDER BY on non-key attributes. To efficiently retrieve top scores, a global secondary index (GSI) with game_id as partition key and score as sort key allows descending queries. Option B is wrong because using scan with limit is inefficient. Option C is wrong because reading all items in the game partition and sorting in application is costly. Option D is wrong because a local secondary index (LSI) would require the same partition key but cannot have a different sort key if the table's sort key is player_id; also LSIs have size limits.
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.
✗
Query the table by game_id and sort the results in the application
Why it's wrong here
All items in the partition are read; sorting in app is wasteful.
✗
Use a Scan operation with a filter expression and limit 10
Why it's wrong here
Scan reads all items and is inefficient and expensive.
✗
Create a local secondary index with partition key game_id and sort key score
Why it's wrong here
LSI requires the same partition key but different sort key; however, it shares table's RCU/WCU and has a 10 GB limit per partition key.
✓
Create a global secondary index with partition key game_id and sort key score
Why this is correct
Query the GSI with ScanIndexForward=false and limit 10 for fast retrieval.
Related concept
Static NAT maps one inside address to one outside address.
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 DBS-C01 NAT questions on configuration and troubleshooting.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create a global secondary index with partition key game_id and sort key score — DynamoDB does not support ORDER BY on non-key attributes. To efficiently retrieve top scores, a global secondary index (GSI) with game_id as partition key and score as sort key allows descending queries. Option B is wrong because using scan with limit is inefficient. Option C is wrong because reading all items in the game partition and sorting in application is costly. Option D is wrong because a local secondary index (LSI) would require the same partition key but cannot have a different sort key if the table's sort key is player_id; also LSIs have size limits.
What should I do if I get this DBS-C01 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 DBS-C01 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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