with sharing, inherited sharing, and User-Mode Operations

public with sharing class AccountController {
    // record-level sharing rules ARE enforced for queries/DML in this class
}

public without sharing class AdminUtility {
    // record-level sharing rules are deliberately bypassed here
}

with sharing enforces the running user's record-level sharing rules for queries and DML inside that class. without sharing deliberately bypasses them — a choice that should be rare, explicit, and well-justified (e.g. a controller that genuinely needs to check something outside the user's normal visibility), never a default reached for out of convenience.

public inherited sharing class RecordFormatter {
    // runs with sharing enforced if its CALLER does; without, if the caller doesn't
}

A class with no sharing keyword has genuinely ambiguous behavior — it depends on context in ways that are easy to get wrong. inherited sharing makes this explicit: the class runs in whatever sharing mode its caller is running in. This matters most for reusable utility classes that might be called from both with sharing and without sharing contexts — the utility shouldn't silently override its caller's security posture either way.

List<Account> accounts = Database.query(
    'SELECT Id, Name FROM Account',
    AccessLevel.USER_MODE
);

Database.insert(newAccount, AccessLevel.USER_MODE);

Passing AccessLevel.USER_MODE to a Database method enforces CRUD, FLS, and sharing together for that single operation — a stronger, more complete guarantee than with sharing alone, which only governs record-level sharing, not field-level security. This is now the recommended default for Apex exposed to LWC, since it matches the same full enforcement LDS already provides automatically (Lesson 1).