When you need to retrieve the total count of records in a large dataset (millions of records), a SOQL aggregate query using COUNT() (Option A) is the most efficient and performant method. Salesforce optimizes aggregate functions at the database 13level. Unlike a standard query that returns in14dividual records and counts against the "50,000 SOQL rows" limit, a COUNT() query returns a single integ15er result and counts as only one row to16ward the governor limits.17

This allows a developer to count millions of records in a single synchronous transactio18n without hitting row limits or causing significant CPU time issues. Option D (SOQL for loop) is the worst approach, as it would attempt to load every individual record into memory, hitting the 50,000-row limit almost immediately and likely causing a LimitException or Request Timeout.

Option B (Batch Apex) is unnecessary for a simple count and is much slower because it runs asynchronously. Option C (SUM) is used for adding up values in numeric fields, not for counting the number of records. For high-volume record counting, SELECT COUNT(Id) FROM Opportunity is the platform-standard approach to provide data to a Lightning component efficiently.