Question 626 of 966

Prepare the data →hardMultiple SelectObjective-mapped

PL-300 Prepare the data Practice Question

This PL-300 practice question tests your understanding of prepare the data. 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.

Which TWO are best practices for optimizing Power Query performance? (Choose two.)

Clue words in this question

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

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

A
Disable the 'Enable background refresh' option in the query settings.
Disabling background refresh can improve performance by preventing simultaneous refreshes.
B
Merge tables as early as possible in the query to combine data.
Why wrong: Merging early may cause large data volumes to be processed; delay merging if possible.
C
Keep all columns in the table to avoid missing data.
Why wrong: Removing unnecessary columns reduces memory and processing time.
D
Filter data as early as possible in the query to reduce row counts.
Early filtering reduces the amount of data carried through subsequent steps.
E
Split columns by delimiter to normalize data.
Why wrong: Splitting columns increases the number of columns and processing steps, potentially reducing performance.

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

✓

Disable the 'Enable background refresh' option in the query settings.

Option A is correct because disabling 'Enable background refresh' prevents Power Query from running queries in the background while you continue working in Power BI Desktop. This ensures that query execution is synchronous, which can improve performance by avoiding resource contention and allowing you to monitor progress directly. Background refresh can cause delays and unexpected behavior when multiple queries run simultaneously, especially with large data sources.

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.

✓
Disable the 'Enable background refresh' option in the query settings.
Why this is correct
Disabling background refresh can improve performance by preventing simultaneous refreshes.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Merge tables as early as possible in the query to combine data.
Why it's wrong here
Merging early may cause large data volumes to be processed; delay merging if possible.
✗
Keep all columns in the table to avoid missing data.
Why it's wrong here
Removing unnecessary columns reduces memory and processing time.
✓
Filter data as early as possible in the query to reduce row counts.
Why this is correct
Early filtering reduces the amount of data carried through subsequent steps.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Split columns by delimiter to normalize data.
Why it's wrong here
Splitting columns increases the number of columns and processing steps, potentially reducing performance.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse data transformation best practices (like merging or splitting columns) with performance optimization techniques, leading them to select options B or E instead of focusing on reducing data volume and controlling query execution.

Detailed technical explanation

How to think about this question

Under the hood, Power Query uses the M language and the mashup engine to evaluate queries. Disabling background refresh forces the engine to execute queries in the foreground, which can be beneficial when you need to control the order of execution or when dealing with data sources that have limited concurrency. A real-world scenario is when you have multiple queries referencing the same source; background refresh might cause them to run simultaneously, overwhelming the source or causing locking issues. Filtering early leverages query folding to push operations back to the source database, reducing the amount of data transferred over the network and processed in memory.

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.

Visual reference

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 PL-300 question test?

Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Disable the 'Enable background refresh' option in the query settings. — Option A is correct because disabling 'Enable background refresh' prevents Power Query from running queries in the background while you continue working in Power BI Desktop. This ensures that query execution is synchronous, which can improve performance by avoiding resource contention and allowing you to monitor progress directly. Background refresh can cause delays and unexpected behavior when multiple queries run simultaneously, especially with large data sources.

What should I do if I get this PL-300 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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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