The two queries that are optimized for large data volumes are: SELECT Id FROM Account WHERE Name != '' AND Customer_Number__c = 'ValueA', and SELECT Id FROM Account WHERE Id IN :aListVariable. An optimized query for large data volumes is a query that filters the records based on an indexed field or a field that has high selectivity. An indexed field is a field that has an index created by the system or the user to speed up the query performance. A field has high selectivity if the filter value in the query matches a low percentage of the total number of records for that object. The Customer_Number__c and Id fields are indexed fields, as they are custom fields that are marked as External Id, which creates an index. The Name field is also an indexed field, except when it is used with the LIKE operator. The != operator and the IN operator are selective operators, as they filter the records based on exact or list values, which can improve the selectivity. The AND operator allows the query to combine multiple filters, which can also improve the selectivity. The query SELECT Id FROM Account WHERE Name LIKE '!-NULL' is not an optimized query for large data volumes, as the LIKE operator with a wildcard character (%) at the beginning of the filter value is not selective, and the Name field is not indexed when used with the LIKE operator. The query SELECT Id FROM Account WHERE Name != '' AND IsDeleted = false is not an optimized query for large data volumes, as the IsDeleted field is not an indexed field, and the false value is not a selective value, as it matches a high percentage of the records. Reference: [Working with Very Large SOQL Queries], [Custom Field Attributes]