SF-PD2 Practice Test 3 — 10 Questions

Question 1

A developer needs to debug an Apex trigger that intermittently fails in production with a 'UNABLE_TO_LOCK_ROW' error when multiple users update related records. Which technique should the developer use to capture the detailed execution context and identify the conflicting transaction?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Enable debug logs for the triggering user and analyze the log for the row lock error and preceding DML operations.. Debug logs are the primary tool for diagnosing runtime errors like UNABLE_TO_LOCK_ROW. They record the exact DML operations and the order in which they occurred, including the records involved. By enabling a debug log for the affected user, the developer can see which DML statement failed to acquire a lock and what operations preceded it. This information is critical to identify the conflicting transaction and refactor the code to avoid locking contention.

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Run the Apex Test Execution with 'Always Run Asynchronously' enabled to simulate concurrent updates.

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Set up a custom logging object and insert a record at the start of each trigger invocation to track user activity.

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Use the Developer Console's Query Plan tool to analyze the selectivity of the SOQL queries in the trigger.

Question 2

A developer is building a Lightning Web Component that needs to display a formatted date and time based on the user's timezone. Which standard JavaScript object, compatible with LWC, should be used to handle this without additional libraries?

Accepted Answer

Intl.DateTimeFormat. Modern browsers and the LWC environment support the Internationalization API (Intl). This built-in JavaScript object provides robust capabilities for formatting dates, numbers, and currencies according to specific locales and timezones. Using standard APIs is preferred over third-party libraries for better performance and reduced bundle size.

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Moment.js

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Date.toGMTString()

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System.now().format()

Question 3

A developer is building a Lightning Web Component that must call an Apex method that performs a callout. The component is placed on a Lightning record page, and the Apex method is annotated with @AuraEnabled(cacheable=true). Users report that the callout never executes and an error is thrown. What is the most likely cause and the correct fix?

Accepted Answer

The callout is blocked because @AuraEnabled(cacheable=true) methods cannot perform callouts; remove cacheable=true or move the callout to a method without caching.. Apex methods annotated with @AuraEnabled(cacheable=true) run in a read-only context that prohibits callouts and DML. When such a method attempts a callout, Salesforce throws an error before the callout is made. The correct resolution is to remove cacheable=true or to move the callout into a separate non-cacheable method that the component invokes directly, allowing the callout to proceed while keeping any cacheable read logic separate.

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The callout is blocked by the component's Lightning locker service; disable locker service for the component in Setup.

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The error occurs because the Apex method must be annotated with @AuraEnabled(cacheable=true) to allow callouts; add the annotation.

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The callout fails because Lightning Web Components cannot call Apex methods that perform callouts; use a Visualforce remoting call instead.

Question 4

An enterprise application requires integrating an external REST API that frequently times out. A developer needs to implement a robust outbound callout mechanism in Apex that handles asynchronous execution while supporting complex retry policies and transactional state management. Which architectural approach best meets these requirements?

Accepted Answer

Create a Queueable Apex class implementing Database.AllowsCallouts, leveraging custom retry logic and job chaining when a timeout occurs.. Queueable Apex implementing Database.AllowsCallouts is the optimal choice for asynchronous HTTP callouts in Salesforce. It supports chaining jobs, passing complex data types as member variables, and provides robust error handling compared to future methods. Mastering asynchronous processing patterns ensures application resilience and prevents governor limit violations during high-volume enterprise integrations.

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Write a @future(callout=true) method that processes the request and executes a synchronous retry loop upon catching a timeout exception.

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Implement a Schedulable class that executes every minute, querying an integration staging table and performing synchronous HTTP callouts.

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Use an InvocableMethod inside a Flow to invoke a synchronous callout immediately when the user updates the source record.

Question 5

A developer is optimizing a Visualforce page that displays a list of accounts with their related contacts. The page uses a standard controller with an extension and a repeater component. The developer notices that the page is slow when there are many accounts, each with several contacts. What is the most likely cause of the performance issue?

Accepted Answer

The extension is querying contacts for each account inside a loop, causing a query per account.. The most likely cause is the N+1 query problem, where the extension queries contacts for each account individually. This results in many SOQL queries, slowing down the page and risking governor limits. The solution is to query all contacts in a single query and then associate them with accounts in memory, or use a relationship subquery. This reduces the number of queries to one or two, improving performance.

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The page is not using JavaScript remoting for data retrieval.

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The page is using a standard controller without a custom extension.

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The page is using a repeater component instead of a data table.

Question 6

A developer is optimizing a Lightning Web Component that displays a list of 500 custom object records. The component uses a wire adapter to call an Apex method that returns the records. The Apex method currently queries all fields on the custom object, including several rich text fields and formula fields that are not displayed in the component. Users report that the component takes a long time to load. What should the developer do to improve the performance of the Apex method?

Accepted Answer

Use a SOQL query that selects only the fields required by the Lightning Web Component, avoiding unnecessary fields.. The Apex method is slow because it queries all fields, including expensive rich text and formula fields that are not displayed. Selecting only the required fields reduces the data volume and computation, improving performance. Caching or limiting records does not address the root cause and may alter functionality. The best solution is to optimize the SOQL query to fetch only the needed fields.

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Use a SOQL query with a LIMIT clause to reduce the number of records returned to 100.

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Use the @AuraEnabled(cacheable=true) annotation on the Apex method to enable client-side caching.

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Increase the cacheable scope of the Apex method to 'global' to cache the results across all users.

Question 7

Refer to the exhibit. A deployment is failing with this error. What is the most likely cause?

Accepted Answer

The custom field is not in the deployment package.. The error indicates a metadata mismatch between the source and target environments. The code references a field that hasn't been deployed or is missing from the target. A successful deployment requires all dependencies, including custom fields and objects, to be present in the target org. Proper tracking of metadata dependencies is essential for avoiding these common deployment failures and ensuring code compatibility across different environments.

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The user performing the deployment lacks field-level security.

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The Apex class was compiled in the wrong API version.

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The custom field needs to be marked as 'Required'.

Question 8

A developer is building a Lightning web component that needs to display a list of accounts with their related contacts. The component uses a wire adapter to call an Apex method that returns a list of Account objects with a nested list of Contacts. The developer notices that the contacts are not displayed, and the Apex method returns the accounts correctly. What is the most likely cause?

Accepted Answer

The Apex method does not query the related contacts using a subquery or separate query, so the contact data is not included in the result.. The most likely cause is that the Apex method's SOQL query does not include the related contacts. To return parent-child data, the query must use a subquery or a separate query to fetch contacts. Without that, the contacts list will be empty. The wire adapter and component can handle nested data, but the data must be present in the Apex result. Ensuring the query includes the child records resolves the issue.

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The Apex method returns a list of Account objects, but Lightning web components cannot handle nested objects in wire adapters.

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The Lightning web component does not use the @wire decorator correctly, so the data is not reactive.

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The Apex method does not use the @AuraEnabled(cacheable=true) annotation, so the wire adapter cannot cache the data.

Question 9

A developer is designing a solution where an external system must be notified in near real-time when a custom object record is created or updated. The external system exposes a REST endpoint that accepts JSON payloads. The solution must be scalable and minimize Salesforce governor limit consumption. Which approach is most appropriate?

Accepted Answer

Use Platform Events to publish an event when the record changes, and have an external subscriber listen and call the external endpoint.. Platform Events enable a scalable, asynchronous, near real-time integration pattern. Publishing an event from Salesforce and having the external system subscribe decouples the systems and avoids governor limit issues. Synchronous callouts in triggers are risky, Batch Apex is not near real-time, and Outbound Messages are SOAP-based and less flexible. The event-driven approach is the most appropriate for this scenario.

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Use Outbound Messages to send the record data to the external endpoint.

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Create a trigger on the custom object that makes a synchronous callout to the external endpoint.

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Schedule a Batch Apex job to run every 5 minutes to query updated records and call the external endpoint.

Question 10

A developer is writing a test class for an Apex trigger that performs a callout. The developer uses a mock class implementing HttpCalloutMock. What happens if the developer fails to implement the mock interface correctly?

Accepted Answer

The test will throw a CalloutException when the trigger code attempts to invoke the HTTP method.. Apex code cannot perform real HTTP callouts during unit tests; Salesforce enforces this to prevent unpredictable external side effects. If the mock interface is not implemented or registered properly using Test.setMock, the system throws a CalloutException. Understanding this mechanism is vital for building robust integration tests, ensuring that external dependency behavior is deterministic and verifiable without hitting actual production endpoints during development cycles.

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The test class will execute the real callout successfully if the endpoint is whitelisted in Remote Site Settings.

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The trigger will process the callout using the default settings defined in Named Credentials.

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The system will automatically generate a mock response based on the WSDL or OpenApi schema.