To implement custom logic for selecting an inventory source, the correct Adobe Commerce development pattern is to create a new Source Selection Algorithm (SSA). This involves creating a new module that implements the Magento\InventorySourceSelectionApi\Api\SourceSelectionInterface. The custom logic, which in this case would calculate the best source based on shipping address and delivery cost, is placed within the execute() method of this implementation. The new algorithm must then be registered with the system using dependency injection by adding it to the sourceSelectionAlgorithms list in a di.xml file.

B: The Distance Priority Algorithm only considers geographic distance, not delivery cost. The PlaceReservationsForSalesEventInterface is used for creating inventory reservations after a source has been selected, not for the selection logic itself.

C: The Source Priority Algorithm uses a pre-configured, static priority of sources and does not dynamically evaluate criteria like shipping address or cost. GetSourceSelectionAlgorithmList is a method to retrieve existing algorithms, not implement a new one.

1. Adobe Commerce Developer Documentation

"Create a custom algorithm": "To create a custom source selection algorithm

you must create a module that implements the SourceSelectionInterface and register it in the di.xml file." This directly supports option A as the correct procedure.

Source: Adobe Commerce Developer Documentation > Inventory Management > Source selection > Create a custom algorithm.

2. Adobe Commerce Developer Documentation

"Source Selection Interface": The documentation for the Magento\InventorySourceSelectionApi\Api\SourceSelectionInterface specifies that it is the contract for Source Selection Algorithms. Any custom algorithm must implement this interface.

Source: Adobe Commerce Developer Documentation > Technical resources > Magento\InventorySourceSelectionApi\Api\SourceSelectionInterface.

3. Adobe Commerce Developer Documentation

"Distance Priority Algorithm": This document explains that the algorithm "calculates the distance between the shipping destination address and source locations" to determine the closest source. It makes no mention of incorporating delivery cost

confirming it does not meet the full requirement.

Source: Adobe Commerce Developer Documentation > Inventory Management > Distance Priority Algorithm.

A virtual type is a dependency injection (DI) configuration that defines a subclass in di.xml without requiring a physical PHP class file. Its primary purpose is to change the constructor arguments for an existing class for a specific injection context. In this scenario, a global preference could conflict with the legacy extension. A virtual type allows the developer to create a specific configuration of a core class (e.g., a service in the checkout process) and inject their new custom tax calculator into it. This targets the change precisely to the checkout process, avoiding global modifications and ensuring the new logic coexists with core and legacy calculations without altering their code.

A. Constructor arguments: This is a general DI feature for defining a class's dependencies, not the specific mechanism for substituting one implementation for another in a targeted way, which is required here.

C. Preferences: A preference creates a global override for a class or interface. This is too broad and would likely conflict with the existing legacy extension or have unintended side effects in other areas.

1. Adobe Commerce Developer Guide

"Virtual types": "Use a virtual type to change the arguments of a specific class dependency. This is useful when you want to inject a different version of a class into a specific object

without affecting other objects that use the same class." This directly supports using a virtual type for a targeted change

as required by the scenario.

Source: Adobe Commerce Developer Documentation

Fundamentals > Dependency injection > Virtual types.

2. Adobe Commerce Developer Guide

"Preferences": "A preference is a global override. When you declare a preference

it affects all instantiations of that class." This explains why a preference is unsuitable for this scenario

as a global change could break the legacy extension's functionality.

Source: Adobe Commerce Developer Documentation

Fundamentals > Dependency injection > Preferences.

3. Adobe Commerce Developer Guide

"Object management": The documentation on DI illustrates that while constructor arguments are fundamental

mechanisms like virtual types and plugins are provided for more complex customization scenarios

such as altering dependencies for specific consumers without modifying their code.

Source: Adobe Commerce Developer Documentation

Fundamentals > Architectural layers > Object management.

By default, HTTP reverse-proxy caches, such as Varnish (which is integral to Adobe Commerce), are configured to cache only "safe" and "idempotent" requests. The HTTP GET and HEAD methods are considered safe as they are intended only for data retrieval and should not alter the server's state. In contrast, HTTP POST and PUT methods are designed to modify data or create resources on the server. Because these actions change the state of the application, their responses are not considered cacheable by default to prevent serving stale or incorrect data. Therefore, if a custom API uses POST or PUT for an operation that should be returning cacheable data, Varnish will bypass the cache, leading to performance delays.

A. The request is using HTTP GET.

Incorrect. GET requests are idempotent and safe, meaning they are designed for data retrieval and are cacheable by default by Varnish and other HTTP caches.

B. The request is using HTTP HEAD.

Incorrect. HEAD requests are functionally similar to GET but without the response body. They are also considered safe and are cacheable by default.

1. Adobe Commerce Developer Documentation - Configure Varnish: The default Varnish Configuration Language (VCL) file provided for Adobe Commerce explicitly bypasses the cache for requests that are not GET or HEAD. The logic in the vclrecv subroutine typically includes a condition like: if (req.method != "GET" && req.method != "HEAD") { return (pass); }. This pass directive instructs Varnish to send the request directly to the backend

bypassing any cache lookup.

Source: Adobe Commerce Developer Documentation

"Get the Varnish VCL file". The default VCL files for various Varnish versions can be found in the magento/magento2 repository under app/code/Magento/PageCache/etc/varnish/.

2. RFC 7231 - Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content: This specification defines the cacheability of different HTTP methods.

Section 4.3.3 (POST): "Responses to POST requests are only cacheable when they include explicit freshness information... However

POST caching is not widely implemented." In practice

caches like Varnish do not cache POST by default.

Section 4.3.4 (PUT): The specification implies non-cacheability as it modifies a resource. Caching a response to a state-changing request is generally unsafe.

Section 4.3.1 (GET): "Responses to GET requests are cacheable..."

Source: IETF RFC 7231

Sections 4.3.1

4.3.3

4.3.4. (DOI not applicable for RFCs

can be found at https://datatracker.ietf.org/doc/html/rfc7231).

The cspwhitelist.xml file is used to define Content Security Policies (CSPs) in Adobe Commerce. To specifically allow images from an external domain, the img-src directive must be used. This directive restricts the URLs from which images can be loaded on a page. Option B correctly uses the node to target only image resources. By adding the external domain website.com as a host type value within this policy, it precisely fulfills the requirement without unnecessarily loosening security for other resource types like scripts or styles, thus maintaining strict policies elsewhere.

A. The media-src directive is incorrect as it is used to specify valid sources for media elements like

C. The default-src directive is incorrect because it serves as a fallback for many other CSP directives. Using it would allow website.com as a source for scripts, styles, fonts, and more, which violates the requirement to maintain strict policies for other resources.

1. Adobe Commerce Developer Documentation

"Content Security Policies": This document explicitly details the configuration of CSPs using cspwhitelist.xml. It provides examples showing the correct XML structure and lists img-src as the directive for defining valid sources for images.

Section: Whitelist a resource

Reference: "To whitelist a resource

you must create a cspwhitelist.xml file... The following example adds a policy for the script-src fetch directive..." (The structure shown is identical to the correct answer

just with a different directive).

2. Adobe Commerce Developer Documentation

"Content Security Policies": The same document provides a table of common CSP directives and their purposes.

Section: Common directives

Reference: The table defines img-src as for "images and favicons

" media-src for "

" and default-src as a "fallback for the other fetch directives

" confirming the specific and correct use of img-src for this scenario.

The n+1 problem is a performance anti-pattern characterized by making one initial query to fetch a list of items, followed by N separate queries to fetch related data for each item. API Mesh directly addresses this inefficiency through its batching capability. By configuring a batching strategy in the mesh source handler, a developer can instruct API Mesh to collect multiple individual requests for related data and combine them into a single, consolidated upstream API call. This significantly reduces the number of network round-trips, directly resolving the n+1 problem and improving application performance.

A. API Mesh unifies existing APIs under a single GraphQL endpoint; it does not replace them. This describes its function, not the solution to the n+1 problem.

C. This is a high-level description of API Mesh's purpose. It is not the specific implementation detail that solves the n+1 performance issue.

1. Adobe. (n.d.). GraphQL source handler. Adobe Developer Documentation. Retrieved from https://developer.adobe.com/graphql-mesh-gateway/mesh/sources/graphql/. In the "Batching" section

the documentation explicitly describes how to use the batch property to "batch multiple calls to the same source into a single call

" which is the direct technical solution to the n+1 problem.

2. Adobe. (n.d.). API Mesh overview. Adobe Developer Documentation. Retrieved from https://developer.adobe.com/graphql-mesh-gateway/. The overview states that API Mesh "reduces the number of API requests that a client application needs to make

" which is the fundamental goal when solving the n+1 problem.

3. Adobe. (2023). API Mesh. Adobe Commerce Developer Guide. Retrieved from https://developer.adobe.com/commerce/extensibility/api-mesh/. This guide highlights that a key benefit of API Mesh is to "improve storefront performance" by combining services

thus preventing the multiple

inefficient API calls characteristic of the n+1 pattern.

In Adobe Commerce, the scope for product pricing is set at the 'Website' level. To achieve independent pricing for different sites while sharing the same underlying product catalog, each site must be configured as a separate Website. A functional storefront requires the complete hierarchy of Website, Store, and Store View. Therefore, the minimum structure is multiple websites, with each website containing its own store and at least one store view. This configuration allows an administrator to set a different price for the same product SKU on each distinct website.

A. Multiple stores and a single store view for each store: This is incorrect because multiple stores under a single website inherit the same pricing configuration from that parent website, failing the requirement for independent price control.

B. One website, one store, and multiple store views: This setup is used for offering a single store in multiple languages. All store views share the same pricing, currency, and customer data from the parent website.

1. Adobe Commerce Developer Documentation

"Attribute Scopes": This document explicitly lists the price attribute as having a scope of Website. It states

"A value entered at the website level overrides the value entered at the global level." This confirms that independent pricing requires separate websites.

Source: Adobe Commerce Developer Guide > Catalog > Product attributes > Attribute scopes.

2. Adobe Commerce User Guide

"Websites

stores

& views": This guide details the hierarchy. It clarifies that a website is the top-level container and is the level at which you can manage different pricing and currencies. It states

"All stores within the same website share the same customer data... and the same prices and currency." This directly supports that different prices require different websites.

Source: Adobe Commerce User Guide > Getting Started > Basic Configuration > Websites

stores

& views.

3. Adobe Commerce Developer Documentation

"Scopes": This document explains the architectural concept of scopes. It defines the Website scope as the level for managing "prices

taxes

payment and shipping methods." This reinforces that pricing is a website-level concern

making multiple websites necessary for the scenario.

Source: Adobe Commerce Developer Guide > Development > Basic concepts > Scopes.

Expanding an Adobe Commerce instance by adding websites, SKUs, and customer groups introduces significant scalability challenges. The platform's EAV (Entity-Attribute-Value) model stores attribute values at different scopes (global, website, store view). Adding new websites for different countries necessitates website-scoped attributes (e.g., price, tax class), which directly increases the size of catalog data tables (B). This data growth, combined with more stores, directly impacts performance. The indexing process, which is crucial for frontend performance, will take longer as it must process data for each additional store. Consequently, database queries for non-cached pages become more complex and slower, leading to increased response times (C).

A. Recreate hierarchy navigation for every new website.

This is not a mandatory issue. A new website requires a root category, but you can create a new one or assign an existing one. The entire hierarchy does not necessarily need to be recreated.

D. Multiple websites may require duplicating custom functionality for each store, which increases code redundancy.

This describes poor development practice, not an inherent architectural issue. Well-designed modules are configured per website/store; the core code is not duplicated, thus avoiding redundancy.

1. Adobe Commerce Developer Documentation

"Performance Best Practices > Database optimization": This guide discusses the impact of catalog size on performance. It states

"The number of products has a direct impact on the catalog browsing performance... The number of websites

stores

and store views also affects performance because it relates to the number of scopes in your system." This supports that adding websites and SKUs (expanding the catalog) impacts performance

validating answers B and C.

2. Adobe Commerce Developer Documentation

"PHP Developer Guide > Architecture > Scopes": This section explains how data for entities like products and categories can be set at different scopes (global

website

store view). It details how website-level scope allows for different pricing or product availability per website

which directly leads to an expansion of catalog data as new websites are added. This validates answer B.

3. Adobe Commerce Developer Documentation

"PHP Developer Guide > Indexing": The documentation explains

"Each indexer can perform one of the following reindex types: Full reindex... Partial reindex...". A larger catalog with more stores and SKUs increases the amount of data to be processed during both full and partial reindexing

making the process longer. This directly supports answer C.

To configure Adobe Commerce to consume messages from a RabbitMQ queue, two primary configuration files are necessary. The queuetopology.xml file is used to declare the message queue infrastructure, including the exchange, the queue itself, and the binding that connects them. This directly addresses the requirement to "configure a local queue." The queueconsumer.xml file then defines the consumer process, linking the previously declared queue to a specific handler class that will process the incoming messages. This fulfills the requirement to "consume messages." Together, these two files provide the complete configuration for a message consumer.

queuepublisher.xml is used for configuring how to publish (send) messages to an exchange, not for consuming them as required by the scenario.

communication.xml defines communication topics and specifies whether they are synchronous or asynchronous, but it does not configure the queue or the consumer itself.

1. Adobe Commerce Developer Documentation

"Configure message queues": This document explicitly details the roles of the configuration files. It states

"Use queuetopology.xml to define the message routing rules and declare queues and exchanges" and "Use queueconsumer.xml to define the relationship between an existing queue and its consumer." This directly supports that these two files are required for the task.

Source: Adobe Commerce Developer Documentation

"PHP Development > Message queues > Configure message queues".

2. Adobe Commerce Developer Documentation

"Create a consumer": This tutorial provides a step-by-step guide. Step 2 is "Define the queue consumer in queueconsumer.xml

" and Step 3 is "Define the queue topology in queuetopology.xml." This confirms these are the essential files for creating a consumer.

Source: Adobe Commerce Developer Documentation

"PHP Development > Message queues > Create a consumer".

3. Adobe Commerce Developer Documentation

"Message Queues Overview": In the "Configuration files" section

the purpose of each file is described. queuetopology.xml is for defining topology

and queueconsumer.xml is for defining consumers. The description for queuepublisher.xml confirms it is for publishing

making options C and D incorrect.

Source: Adobe Commerce Developer Documentation

"PHP Development > Message queues > Message Queues Overview".

In Adobe Commerce and Magento Open Source, the event-observer pattern is implemented through XML configuration. To subscribe an observer to a specific event, a developer must declare it within the module's etc/events.xml file. This file maps the event name (e.g., customerregistersuccess) to a specific observer class. The configuration specifies the observer's unique name and the class instance that contains the logic to be executed when the event is dispatched by the system. This file can be placed in global (etc/), frontend (etc/frontend/), or admin (etc/adminhtml/) scopes depending on the event's area.

B. Declare in etc/events.xml: This is a duplicate of the correct answer and is therefore also correct. However, in a standard multiple-choice format, only one option is typically selected.

C. Declare in etc/observer.xml: This is incorrect because etc/observer.xml is not a standard configuration file used in Adobe Commerce for declaring observers. The correct and required file name is events.xml.

---

1. Adobe Commerce Developer Documentation

Events and observers: "You declare an observer in the events.xml file. The file can be in the /etc

/etc/frontend

or /etc/adminhtml directory." The documentation provides a specific example for the customerregistersuccess event.

Source: Adobe Commerce Developer Guide > PHP Developer Guide > The Core > Events and observers.

2. Adobe Commerce Developer Documentation

Module configuration files: The official list of module configuration files includes events.xml for "Event configuration" and does not list an observer.xml file.

Source: Adobe Commerce Developer Guide > PHP Developer Guide > The Core > Modules > Module configuration files.

After deciding to use an extension attribute, you must register it with the service-contract data interface and then populate it at runtime.

1. etc/extensionattributes.xml declares the new attribute for Magento\Catalog\Api\Data\ProductInterface so that it becomes part of every service contract response (REST, SOAP, export, etc.).

2. An after-plugin on Magento\Catalog\Api\ProductRepositoryInterface::get() / ::getList() hydrates the attribute with the calculated lifetime-sales value before the data object is returned, ensuring it is visible both in API payloads and in exports.

A. etc/webapirest/extensionattributes.xml is not used; extensionattributes.xml at the module root is sufficient for all service-contract transports.

B. Around plugins wrap the whole call and add avoidable overhead; Magento’s own guide recommends after plugins for adding data to a returned entity.

1. Adobe Commerce DevDocs v2.4

“Service Contracts – Extension Attributes”

§Declare extension attributes

para 1-3.

https://developer.adobe.com/commerce/php/2.4/developer-guide/service-contracts/extension-attributes/#declare-extension-attributes

2. Adobe Commerce DevDocs v2.4

“Service Contracts – Extension Attributes”

§Load and save extension attribute values

example uses afterGet/afterGetList plugins.

Same URL

para 5-8.

3. Adobe Commerce DevDocs v2.4

“Plugins”

§Best practices

bullet 2: prefer after plugins to around unless modification of call flow is required.

https://developer.adobe.com/commerce/php/2.4/developer-guide/plugins/