SALESFORCE-PD1 Developer Fundamentals Practice Question
An Apex trigger needs to prevent duplicate records from being inserted based on a custom external ID field. Which approach should the developer take to optimize query performance and respect governor limits?
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
✓
Collect the external ID values into a Set, query once outside the loop, and use a Map for validation.
Collecting field values into a Set, querying existing records matching that Set in a single query outside of loops, and comparing in memory is the bulkified approach.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use Database.upsert with strict mode enabled inside the trigger loop.
Why it's wrong here
Performing DML statements inside trigger loops violates governor limits.
- ✗
Query the database inside a for loop for every record in Trigger.new.
Why it's wrong here
This leads to SOQL limit exceptions.
- ✓
Collect the external ID values into a Set, query once outside the loop, and use a Map for validation.
Why this is correct
This is fully bulkified and avoids governor limit violations.
- ✗
Use an asynchronous @future method to validate duplicates after insert.
Why it's wrong here
Future methods run after insert and cannot prevent the transaction from committing the duplicate records.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Salesforce exam blueprint
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