To optimize a high-volume SOQL query, two primary strategies are essential. First, ensuring the query is selective (C) is critical. A selective query uses indexed fields in its WHERE clause to efficiently narrow down the dataset, preventing the database from scanning all records in the object. This dramatically reduces processing time. Second, queries that involve complex sharing hierarchy calculations (D) are notoriously slow, especially with millions of records. By removing this constraint—for example, by running the query with a user profile that has "View All Data" permissions for the object—the system bypasses these expensive calculations, leading to a significant performance gain.

1. Salesforce Architect Documentation

Architect's Guide to Large Data Volumes:

For C (Selective Criteria): The guide states

"The single most important thing you can do to improve the performance of a SOQL query is to make sure that it is selective." It emphasizes using indexed fields in the WHERE clause. (See section: "Make SOQL Selective").

For D (Sharing Restrictions): The guide explains

"Sharing calculations can be costly... When a query is executed

the platform checks the sharing table... For a user who can see a small subset of the data

this check can be time-consuming." It recommends strategies like using a user with "View All Data" to bypass these checks for integrations. (See section: "Sharing").

2. Salesforce Developer Documentation

SOQL and SOSL Reference:

For C (Selective Criteria): The "Query & Search Optimization Cheat Sheet" details how the Force.com query optimizer uses indexes on fields in WHERE clauses to run queries efficiently. It defines a selective query as one that filters on an indexed field. (See section: "The Force.com Query Optimizer").

3. Salesforce Developer Documentation

Apex Developer Guide:

For C (Selective Criteria): The guide notes

"For best performance

SOQL queries must be selective... To avoid long execution times

the system terminates non-selective SOQL queries." (See Chapter 3

"Database & .NET Concepts

" section: "Working with Very Large SOQL Queries").

For D (Sharing Restrictions): The guide explains the use of with sharing and without sharing keywords

which control the enforcement of sharing rules. Using without sharing can improve performance by not evaluating the organization's sharing model for the current user. (See Chapter 2

"Classes

" section: "Using the with sharing

without sharing

and inherited sharing Keywords").