The most fundamental best practice for writing bulk-safe (scalable) Apex triggers is to avoid performing DML operations or SOQL queries inside of loops. Salesforce enforces a limit of 150 DML statements per transaction. If a trigger iterates through a list of 200 records and performs a delete or update inside that loop, the code will fail with a governor limit exception after the 150th record.

To make a trigger bulk-safe, developers must collect all records that need to be processed into a collection (such as a List or Map) and then perform a single DML operation on that entire collection outside of the loop (Option B). This consumes only one DML statement regardless of the number of records (up to the 10,000 row limit).

Option A is incorrect because LIMIT 50000 does not help with bulk safety; it just prevents a query from exceeding the SOQL row limit. Option C (using allOrNone=false) allows for partial success of a DML operation but does not inherently make a trigger bulk-safe if the calls are still made inside a loop. Option D is incorrect because moving DML to a future method is a way to handle callouts or long-running processes, but it is not a general requirement for trigger bulkification and can lead to reaching asynchronous limits if used incorrectly.

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When developing custom functionality to be surfaced within the standard Salesforce Mobile App, Lightning Web Components (LWC) (Option B) is the recommended approach. LWCs are the modern, high-performance standard for Salesforce development, utilizing modern web standards (ES6+, Web Components) that run natively in the browser.

LWC is preferred over the other options for several reasons:

Performance: LWCs are lightweight and provide a much faster, more responsive user interface than Visualforce (Option D), which is critical for mobile user experience.

Standardization: Since the app will be accessed via the standard Salesforce mobile app, LWCs integrate seamlessly into the mobile navigation, tabs, and action menus.

Customization: LWCs provide full control over the CSS and HTML, allowing the developer to meet the "custom user interface design" requirement while still leveraging the Lightning Data Service for efficient data handling.

Option A (Salesforce SDK) is for building "Custom/Native" standalone apps, not for extending the standard Salesforce app. Option C (Experience Builder) is primarily for external sites (Communities). LWC provides the perfect balance of "custom design" and "native integration" for internal mobile users.

For application configurations that control behavior and styling across different environments, Custom Metadata Types (Option A) are the industry-standard choice. The primary advantage of Custom Metadata over Custom Settings or Custom Objects is tha1t the2 records themselves are treated as metadata. This means they can be deployed using Change Sets, Salesforce CLI, or packages. When a developer moves code from a Sandbox to Production, the associated configuration records are included in the deployment, ensuring that the Lightning Web Component behaves identically in both environments without manual data setup.

Furthermore, Custom Metadata is highly "testable." In Apex unit tests, you can query Custom Metadata records without needing the (SeeAllData=true) annotation. If your component's Apex controller logic depends on these variables, the tests will remain robust and environment-independent. Custom Settings (Option C) and Custom Objects (Option B) store records as data, which cannot be deployed via Change Sets and require manual entry or data loading in every new sandbox or production org, increasing the risk of configuration errors. Custom Metadata provides the most "extendable" and deployable way to manage component-level constants and behavioral flags.