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Question 659 of 1,786

Data Store Management →mediumMultiple ChoiceObjective-mapped

Quick Answer

The dual-write pattern is the correct strategy for migrating Cassandra to Amazon Keyspaces with minimal downtime. This approach works because the application writes to both the on-premises cluster and Keyspaces simultaneously, ensuring continuous data flow while a backfill process loads the existing 10 TB of historical data. Once the backfill completes and both systems are synchronized, reads can be switched to Keyspaces with near-zero interruption, avoiding the extended downtime that bulk export or snapshot restore would require. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of live migration patterns versus batch methods—a common trap is choosing a snapshot-based approach that forces application downtime. Remember that dual-write prioritizes availability over simplicity, making it ideal for production systems where every second of downtime matters. A helpful memory tip: think "write to both, read from one" to recall the dual-write sequence.

DEA-C01 Data Store Management Practice Question

This DEA-C01 practice question tests your understanding of data store management. 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 data engineer is migrating an on-premises Apache Cassandra cluster to Amazon Keyspaces (for Apache Cassandra). The cluster has 10 TB of data. The migration must minimize application downtime. Which strategy should the engineer use?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

Question 1mediummultiple choice

Full question →

A
Set up a dual-write pattern where the application writes to both the on-premises cluster and Keyspaces, then switch reads to Keyspaces once data is synchronized.
This minimizes downtime by keeping both systems in sync and allows for a gradual cutover.
B
Export the data using the Cassandra COPY command and import it into Keyspaces using the COPY command.
Why wrong: The COPY command is not supported in Amazon Keyspaces.
C
Take a snapshot of the on-premises cluster and restore it to Keyspaces using the Keyspaces console.
Why wrong: Snapshots are point-in-time and may not capture recent writes, leading to data loss.
D
Use AWS Database Migration Service (DMS) to continuously replicate data from the on-premises cluster to Keyspaces.
Why wrong: AWS DMS does not support Apache Cassandra as a source.

Full breakdown with real-world context →

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

✓

Set up a dual-write pattern where the application writes to both the on-premises cluster and Keyspaces, then switch reads to Keyspaces once data is synchronized.

Option A is correct because the dual-write pattern allows the application to write to both the on-premises Cassandra cluster and Amazon Keyspaces simultaneously, ensuring data consistency with minimal downtime. Once the existing data is backfilled and the systems are synchronized, reads can be switched to Keyspaces with near-zero application interruption. This approach avoids the downtime required for bulk export/import or snapshot restore.

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.

✓
Set up a dual-write pattern where the application writes to both the on-premises cluster and Keyspaces, then switch reads to Keyspaces once data is synchronized.
Why this is correct
This minimizes downtime by keeping both systems in sync and allows for a gradual cutover.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Export the data using the Cassandra COPY command and import it into Keyspaces using the COPY command.
Why it's wrong here
The COPY command is not supported in Amazon Keyspaces.
✗
Take a snapshot of the on-premises cluster and restore it to Keyspaces using the Keyspaces console.
Why it's wrong here
Snapshots are point-in-time and may not capture recent writes, leading to data loss.
✗
Use AWS Database Migration Service (DMS) to continuously replicate data from the on-premises cluster to Keyspaces.
Why it's wrong here
AWS DMS does not support Apache Cassandra as a source.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume AWS DMS can handle any database migration, but DMS does not support Cassandra as a source, making Option D a distractor for those who overestimate DMS's capabilities.

Trap categories for this question

Command / output trap
The COPY command is not supported in Amazon Keyspaces.

Detailed technical explanation

How to think about this question

The dual-write pattern leverages Cassandra's lightweight transactions or idempotent writes to maintain consistency across two clusters during migration. Under the hood, the application must handle write failures gracefully and use a backfill process (e.g., with Spark or a custom script) to migrate existing data while new writes are dual-routed. In a real-world scenario, this pattern is critical for large-scale migrations where even minutes of downtime can cause significant business impact.

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 DEA-C01 question test?

Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Set up a dual-write pattern where the application writes to both the on-premises cluster and Keyspaces, then switch reads to Keyspaces once data is synchronized. — Option A is correct because the dual-write pattern allows the application to write to both the on-premises Cassandra cluster and Amazon Keyspaces simultaneously, ensuring data consistency with minimal downtime. Once the existing data is backfilled and the systems are synchronized, reads can be switched to Keyspaces with near-zero application interruption. This approach avoids the downtime required for bulk export/import or snapshot restore.

What should I do if I get this DEA-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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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