- A
Increase the RCUs to 100.
Why wrong: Increasing RCUs increases throughput but does not reduce latency caused by filter expression on sort key.
- B
Add a random suffix to the partition key values to distribute writes across partitions.
Why wrong: Sharding would scatter data and break the ability to query by player_id efficiently.
- C
Create a Local Secondary Index (LSI) with the same partition key and a sort key of 'session_start_time', and query the index instead of the table.
LSI allows efficient range queries on the sort key without scanning and filtering.
- D
Create a Global Secondary Index (GSI) with partition key 'event_type' and sort key 'session_start_time' and query the GSI.
Why wrong: The query is by player_id, not event_type, so this GSI would not help.
Quick Answer
The correct choice is to create a Local Secondary Index (LSI) with the same partition key and a sort key of session_start_time, then query the index instead of the table. This works because an LSI shares the table’s partition key but allows a different sort key, enabling DynamoDB to efficiently retrieve only the items for a specific player within the last 24 hours using the sort key’s range comparison, rather than scanning all sessions for that player and applying a filter. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of how LSIs reduce read consumption by avoiding full partition scans—a common trap is thinking a Global Secondary Index (GSI) is needed, but since the partition key stays the same, an LSI is more cost-effective and consistent. Remember the memory tip: “LSI for same PK, different SK; GSI for different PK entirely.”
DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. 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 gaming company uses Amazon DynamoDB as the primary database for their player sessions. The player sessions table has a partition key of 'player_id' and a sort key of 'session_start_time'. The application frequently queries for recent sessions of a specific player, using the query API with 'player_id' and a filter on 'session_start_time' for the last 24 hours. The average item size is 5 KB. The company notices high latency on these queries during peak hours. The table has 10 Read Capacity Units (RCUs) provisioned. There are no indexes. Which design change would MOST improve query performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"primary"Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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
Create a Local Secondary Index (LSI) with the same partition key and a sort key of 'session_start_time', and query the index instead of the table.
Option C is correct because creating a Local Secondary Index (LSI) with the same partition key (player_id) and sort key (session_start_time) allows DynamoDB to efficiently retrieve items for a specific player sorted by session_start_time without scanning and filtering. The current query uses a filter on session_start_time after retrieving all sessions for the player, which wastes read capacity and increases latency. Querying the LSI directly uses the sort key to limit the data read to only the last 24 hours, reducing the read footprint and improving performance.
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.
- ✗
Increase the RCUs to 100.
Why it's wrong here
Increasing RCUs increases throughput but does not reduce latency caused by filter expression on sort key.
- ✗
Add a random suffix to the partition key values to distribute writes across partitions.
Why it's wrong here
Sharding would scatter data and break the ability to query by player_id efficiently.
- ✓
Create a Local Secondary Index (LSI) with the same partition key and a sort key of 'session_start_time', and query the index instead of the table.
Why this is correct
LSI allows efficient range queries on the sort key without scanning and filtering.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a Global Secondary Index (GSI) with partition key 'event_type' and sort key 'session_start_time' and query the GSI.
Why it's wrong here
The query is by player_id, not event_type, so this GSI would not help.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that simply increasing RCUs (Option A) solves high latency, but the real issue is inefficient data access patterns that waste read capacity, not insufficient throughput.
Detailed technical explanation
How to think about this question
Under the hood, DynamoDB's Query operation with a sort key condition on an LSI uses the index's sorted data structure to directly seek to the relevant items, reading only the required 5 KB items for the last 24 hours. Without an index, the query must read all items for that player_id (potentially many sessions) and then discard those outside the time window, consuming more read capacity and increasing latency. In a real-world scenario, a player might have thousands of sessions, so filtering after retrieval would consume excessive RCUs and cause throttling during peak hours.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a Local Secondary Index (LSI) with the same partition key and a sort key of 'session_start_time', and query the index instead of the table. — Option C is correct because creating a Local Secondary Index (LSI) with the same partition key (player_id) and sort key (session_start_time) allows DynamoDB to efficiently retrieve items for a specific player sorted by session_start_time without scanning and filtering. The current query uses a filter on session_start_time after retrieving all sessions for the player, which wastes read capacity and increases latency. Querying the LSI directly uses the sort key to limit the data read to only the last 24 hours, reducing the read footprint and improving performance.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This DBS-C01 practice question is part of Courseiva's free Amazon Web Services 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 DBS-C01 exam.
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