What is CRUD and FLS enforcement in Apex and how is it implemented?

By default, Apex runs in system context — it bypasses CRUD (object-level) and FLS (field-level) security. To enforce security: CRUD checks: Use Schema methods — Schema.sObjectType.Account.isCreateable(), isReadable(), isUpdateable(), isDeletable() before DML/queries. FLS checks: Schema.sObjectType.Account.fields.Name.isAccessible(), isUpdateable(). Simplified approach: Use Security.stripInaccessible() to automatically strip fields the user cannot access from query results or DML inputs — cleaner than manual field-by-field checks. with sharing: Enforces record-level sharing rules (OWD/role hierarchy) but NOT FLS/CRUD. Always pair sharing enforcement with explicit FLS checks for full security compliance.