Explanation:

Why Tooling API Is the Correct Choice
The Java application needs to run SOQL queries to retrieve and modify individual pieces of Salesforce metadata (such as Apex classes, triggers, custom fields, validation rules, or flows). The Tooling API is the only Salesforce API specifically designed for exactly this purpose: it exposes metadata components as queryable objects, allowing direct SOQL statements like SELECT Id, Name, Body FROM ApexClass or SELECT DeveloperName, TableEnumOrId FROM CustomField, and supports create, update, and delete operations on single components. It is lightweight, fast, and built for programmatic interaction from external tools or custom applications, making it the perfect fit for this scenario.

Why the Other Options Are Incorrect
B. Any Salesforce API is far too broad and incorrect; most Salesforce APIs (REST, SOAP, Bulk, etc.) are designed for record data, not metadata manipulation via SOQL.

C. User Interface API is meant for building custom UIs that mimic Lightning Experience by retrieving layouts, record types, and data—it cannot be used to query or modify metadata components.

D. Metadata API works with large ZIP file packages and package.xml manifests for bulk retrieve/deploy operations; it does not support direct SOQL queries against individual metadata components and is unsuitable for the granular, query-driven approach described.

References
Salesforce Tooling API Developer Guide:
Tooling API Objects Reference (ApexClass, CustomField, etc.)
Trailhead module: “Work with Metadata Using Tooling API”
Salesforce DX Developer Guide – Tooling API vs Metadata API comparison

Explanation:

The primary requirement for a hotfix environment is speed and minimal data. A hotfix typically involves a quick metadata change (Apex, configuration) to resolve an urgent, small issue, and it needs to be promoted to Production as quickly as possible.

B. Developer Sandbox
A Developer Sandbox is highly suitable for hotfixes because it only copies metadata (configuration and code) and has a daily refresh interval.
Speed: Being metadata-only, it has the fastest creation and refresh time, which is critical when a production issue needs immediate attention.
Isolation: It provides a safe, isolated environment (only 200 MB of data storage) to develop and unit test the fix without the overhead of production data.

D. Developer Pro Sandbox
A Developer Pro Sandbox is also appropriate, offering a good balance for hotfixes, especially for slightly more complex issues. It also copies only metadata and has a daily refresh interval.
Storage: It offers 1 GB of data storage (compared to 200 MB for a Developer Sandbox). This extra space can be useful if the hotfix requires creating or loading a small, specific data set to fully reproduce the production issue before the fix can be properly validated.
Speed: Like the Developer Sandbox, the daily refresh and metadata-only copy ensures fast environment availability.

❌ Details of Incorrect Answers
A. Partial Copy Sandbox
Reasoning: A Partial Copy Sandbox copies metadata and a sample of production data (up to 5 GB). While the sample data can be useful for complex testing, its refresh interval is 5 days. This is too long for an urgent hotfix environment, as the environment would be quickly outdated and unavailable for immediate use when a new production issue arises.

C. Full Sandbox
Reasoning: A Full Sandbox is a complete replica of Production, including all data and metadata.
Refresh Time: Its refresh interval is the slowest at 29 days, making it unusable for the high-frequency refresh required to address random, urgent hotfixes.
Cost and Size: It is the most expensive and largest sandbox type, making it inefficient for quick, small-scope hotfix development. Full sandboxes are typically reserved for major release staging, load testing, and UAT.

📘References
Salesforce Documentation: Sandbox Types and Templates
Developer and Developer Pro sandboxes copy metadata only and have a refresh interval of 1 day, making them the fastest and most disposable options for isolated development and fixes.

Partial Copy has a refresh interval of 5 days.
Full Copy has a refresh interval of 29 days.

Salesforce Certified Platform Development Lifecycle and Deployment Architect Guidance
Best practice for hotfixes is to use a rapidly available, metadata-focused environment (Developer or Developer Pro) to minimize development time and avoid waiting for long refresh cycles associated with Partial or Full Sandboxes.

Explanation:

This question addresses a common problem in org management: how to catch issues caused by configuration changes (metadata) before they reach production. The core issue is that administrators are making changes in a higher-level environment (like a UAT or Staging sandbox, or even Production) without a process to validate the impact of those changes on existing code.

Why A is Correct:
Shifts Left the Discovery of the Problem: The goal is to find the issue "earlier." By bringing the permission sets into a version-controlled development pipeline, any change made by an administrator must follow the same path as code.

Automated Testing in CI (Continuous Integration): When the permission sets are committed to source control and go through a CI process, this process can automatically deploy the changes to a testing environment and run the full suite of Apex tests. If a SOQL query fails because it is querying a field that the new permission set no longer grants access to, the Apex test that runs that query will fail during the CI build. This failure will immediately notify the developers of a breaking change.

Provides a Single Source of Truth: This strategy integrates administrative changes (permission sets) into the same governance model as developer changes (Apex, Lightning, etc.). It prevents "metadata drift" and ensures that the state of any environment is defined by a known version in source control.

Proactive, Not Reactive: Instead of discovering failing queries randomly in a shared sandbox or production, this strategy catches the problem in an automated, isolated build environment, allowing it to be fixed before it impacts users or other teams.

Why the Other Options are Incorrect:
B. Ask administrators to only make changes to profiles instead. This is incorrect and a step backwards.
Profiles are More Restrictive: You can only assign one profile per user, but many permission sets. Moving to profiles would reduce flexibility.
It Doesn't Solve the Problem: The same underlying issue would occur. If a profile change removed access to a field, the SOQL queries would still fail. This option just changes the type of metadata causing the problem, not the process flaw.
Best Practice: Salesforce best practice is to use Permission Sets for granting access and Profiles for restricting it.

C. Create a sandbox refresh strategy to ensure each sandbox is refreshed every day. This is incorrect and counterproductive.
Destroys the Environment: Refreshing a sandbox every day would wipe out all ongoing work, including the administrator's changes and any testing data. It creates chaos.
Does Not Catch the Issue: A refresh copies production metadata into the sandbox. If the problematic permission set change has already been deployed to production, refreshing will just bring that broken state into the sandbox, making the problem worse.

D. Advise developers to switch to SOSL queries that are more robust instead. This is technically incorrect and addresses the symptom, not the cause.
SOSL is for Search, not Precision: SOSL (Salesforce Object Search Language) is designed for text-based search across multiple objects. It is not a replacement for SOQL (Salesforce Object Query Language), which is for retrieving specific records from a single object based on precise criteria.
Permission Issue Persists: SOSL queries are also subject to Field-Level Security (FLS). If the user running the query doesn't have FLS access to a field, it will be omitted from the SOSL results, leading to the same type of functional failures.
Poor Architecture: Recommending a wholesale change from a precise query language to a search language due to a process problem is an architectural anti-pattern.

References & Key Concepts for a Lifecycle Architect:
DevOps and CI/CD: The core solution is a DevOps principle: "Everything as Code." This includes configuration and metadata, not just Apex. Integrating all changes into a CI pipeline is the primary mechanism for catching issues early.

Governance: A Lifecycle Architect must design processes that govern all changes to the org, whether made by developers or administrators. Option A establishes this governance.

Testing and Quality Gates: The CI process acts as a quality gate. Automated tests are the checks that run at this gate to validate that new changes (whether code or config) do not break existing functionality.

Source Control Driven Development: The recommended strategy moves the organization towards a model where the source control repository is the single source of truth for the desired state of the org. All changes originate from there.

Explanation

Let’s break down what UC needs:
Weekly training for 4 weeks
Each session lasts 5 days
Trainees work on samples of production data
At the end of each week, all training data should be wiped

UC is on Performance Edition → they have access to Partial Copy and Developer Pro sandboxes

Key Salesforce facts:
Partial Copy Sandbox
Contains a subset of production data, defined by a sandbox template
Refresh interval: 5 days

Developer / Developer Pro Sandbox
Contains no production data by default (only metadata)
Refresh interval: 1 day
Any data needed must be manually loaded (e.g., via Data Loader)

Given that UC wants sample production data and to reset each week, the best flow is:
Use a Partial Copy sandbox with a sandbox template that selects only the relevant objects/data needed for training, then refresh it every weekend.

This will:
Automatically bring in fresh, realistic production-like data each time using the template
Automatically wipe out all training data (anything created/changed during the week) when you refresh
Avoid manual data loading via Data Loader every week

That matches:
✅ B. Refresh a Partial Copy sandbox every weekend and include an appropriate sandbox template.

Why the others are not optimal
A. Partial Copy + load data with Data Loader
Partial Copy already supports bringing in sample production data via templates, so loading via Data Loader is extra manual work you don’t need.

C. Developer Pro + Data Loader
No prod data by default; you must manually load sample data every week.
More effort and more room for mistakes vs automatically pulling from Production with a template.

D. Developer Pro + template
Sandbox templates only apply to Partial Copy and Full sandboxes, not Developer/Dev Pro.
So this option is technically incorrect.

So the optimal architectural recommendation is:
✅ B. Use a Partial Copy sandbox with an appropriate template, refreshed every weekend.

Explanation:

Salesforce operates on a multi-tenant architecture. This means that a single, shared instance of the Salesforce application and database infrastructure hosts the data and configuration for multiple independent customers (tenants).

Impact of Stress Testing: Stress testing is designed to push a system to its breaking point or well beyond its normal operating limits to observe its failure and recovery behavior. If one customer were to intentionally stress-test their Production environment, the massive load and resource consumption could severely degrade the performance, availability, and stability of the shared services for all other customers on that same instance (or "pod").

Fairness and Service Level Agreements (SLAs): To ensure a consistent, high-quality service and uphold SLAs for all customers, Salesforce must strictly govern resource usage. Prohibiting unapproved, resource-intensive activity like stress testing in the live, shared environment is a fundamental protection of the multi-tenant model.

❌ Details of Incorrect Answers
A. There is not enough CPU
While limited CPU resources are the technical consequence of a multi-tenant environment, this is not the fundamental reason for the prohibition. Salesforce ensures there is sufficient CPU capacity for normal operations. The prohibition is because the system must be shared fairly among tenants, and stress testing would violate that fairness, regardless of the overall capacity.

C. It is blocked by data center infrastructure
While Salesforce's infrastructure enforces the policy (through throttling and monitoring), the infrastructure itself is built to handle load spikes. The reason for the block is the architectural model (multi-tenancy), not an inherent limitation of the physical data center hardware.

D. It causes Internet congestion
Internet congestion is typically related to public network bottlenecks outside of the controlled data center environment. Salesforce's prohibition is about internal server-side resource consumption (database queries, CPU, memory) and the impact on co-located tenants, not the external network health.

📘 References
Salesforce Documentation on Performance Testing:
Salesforce explicitly states that performance testing, especially stress or load testing, must be conducted in an isolated environment like a Full Copy Sandbox or using their dedicated Scale Test service.
They emphasize the need for prior approval, often a minimum of two weeks in advance, and explicitly state that testing is not permitted in the production environment.

Salesforce Architect Guidance (Multi-Tenant Architecture):
The core principle of the Salesforce Platform is multi-tenant isolation, which is protected by Governor Limits and resource management rules to ensure the actions of one customer cannot negatively impact others. Stress testing directly attempts to break these limits and is thus prohibited in Production.