Why DynamoDB Scan Returns ScannedCount but Count of 0 with Filter
This DVA-C02 practice question tests your understanding of development with aws services. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
Network Topology
The developer runs a scan on the DynamoDB table 'orders' with a filter expression to find items with order_status equal to 'SHIPPED'. The output shows ScannedCount of 10000 but Count of 0. Which statement is correct?
Network Topology
A
The scan retrieved 10,000 items from the table, but none matched the filter condition.
Filter expressions are applied after the scan, so all items were scanned but filtered out.
B
The scan only returned items that matched the filter, so there are no items with status SHIPPED.
Why wrong: Filter expressions do not reduce the scanned count; they only reduce the returned items.
C
The filter expression syntax is incorrect, causing the scan to return zero items.
Why wrong: The syntax is valid; ScannedCount indicates the scan ran successfully.
D
The scan applied the filter before reading items, so only matching items were scanned.
Why wrong: DynamoDB applies filters after reading items from the table.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The scan retrieved 10,000 items from the table, but none matched the filter condition.
In DynamoDB, a Scan operation retrieves all items in the table or index up to the 1 MB limit, then applies any filter expression client-side. The ScannedCount of 10,000 indicates that 10,000 items were read from the table, but the Count of 0 means none of those items satisfied the filter condition (order_status = 'SHIPPED'). This is the expected behavior: filters are applied after the data is read, not before.
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.
✓
The scan retrieved 10,000 items from the table, but none matched the filter condition.
Why this is correct
Filter expressions are applied after the scan, so all items were scanned but filtered out.
Related concept
Read the scenario before looking for a memorised answer.
✗
The scan only returned items that matched the filter, so there are no items with status SHIPPED.
Why it's wrong here
Filter expressions do not reduce the scanned count; they only reduce the returned items.
✗
The filter expression syntax is incorrect, causing the scan to return zero items.
Why it's wrong here
The syntax is valid; ScannedCount indicates the scan ran successfully.
✗
The scan applied the filter before reading items, so only matching items were scanned.
Why it's wrong here
DynamoDB applies filters after reading items from the table.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ScannedCount with Count, assuming that the filter is applied before reading (like a SQL WHERE clause), when in fact DynamoDB scans all items first and then filters, so ScannedCount reflects total items read and Count reflects matches only.
Detailed technical explanation
How to think about this question
Under the hood, DynamoDB's Scan operation reads items in parallel segments across partitions, returning up to 1 MB of data per request. The filter expression is evaluated on the client side after the data is retrieved, meaning you still pay for the read capacity units (RCUs) consumed by all scanned items, not just the filtered results. In real-world scenarios, this can lead to unexpected costs and throttling if a large table is scanned frequently with restrictive filters, as the full dataset is still read.
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.
Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The scan retrieved 10,000 items from the table, but none matched the filter condition. — In DynamoDB, a Scan operation retrieves all items in the table or index up to the 1 MB limit, then applies any filter expression client-side. The ScannedCount of 10,000 indicates that 10,000 items were read from the table, but the Count of 0 means none of those items satisfied the filter condition (order_status = 'SHIPPED'). This is the expected behavior: filters are applied after the data is read, not before.
What should I do if I get this DVA-C02 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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