SF-Data-Arch Large Data Volume Considerations Practice Question
What is a 'Selective Query' in the context of Salesforce LDV?
⚠ Common exam trap
Candidates often confuse 'selective' with 'simple' queries. They fail to understand that selectivity is a mathematical threshold based on the percentage of records returned, not just query complexity.
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
✓
A query that utilizes indexed fields to filter within defined thresholds.
A selective query is one that hits an index and returns a small, efficient subset of records. Salesforce imposes selectivity thresholds; if a query exceeds these (e.g., usually 30% of the first million records), it is considered non-selective. Ensuring queries are selective is the single most important factor in maintaining performance for large datasets, as it allows the database to avoid exhaustive scanning of rows.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A query that uses exactly five fields in the WHERE clause.
Why it's wrong here
Selectivity is not defined by the number of fields in the WHERE clause. It is defined by the underlying data distribution and whether those fields are indexed. A query with five fields could still be non-selective if none of those fields are indexed or if they don't filter enough rows.
- ✗
A query that returns fewer than 100 records total.
Why it's wrong here
The number of records returned is a result of the query, not the definition of selectivity. A query could return 100 records but still be non-selective if the database had to scan the entire 50-million-row table to identify those 100 records because no index was used.
- ✓
A query that utilizes indexed fields to filter within defined thresholds.
Why this is correct
A selective query is one that effectively uses indexes to limit the search space to a small percentage of total records. By staying within the platform's selectivity thresholds, the query optimizer can retrieve results quickly without the performance penalty associated with full table scans on massive data sets.
- ✗
A query that uses only SOQL and no Apex logic.
Why it's wrong here
The presence or absence of Apex logic has no impact on query selectivity. Selectivity is entirely dependent on the database layer's ability to efficiently find data based on filters. Whether a query is run in Apex or via a tool, the underlying database execution remains the same.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Salesforce exam blueprint
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