Salesforce Platform Developer II Study Guide (Winter '26): Complete PD2 Exam Prep

Design Patterns (25%)

The foundation of PD2. Apex Enterprise Patterns (AEP): Selector layer (all SOQL queries — centralises data access, enforces field-level security checks), Domain layer (business logic tied to an SObject type — validates, defaults, and enriches records), Service layer (orchestrates business processes across multiple objects), Unit of Work (manages all DML in bulk at the end of a transaction to prevent partial commits and governor limit issues). Other patterns: Singleton (prevent duplicate initialisation of expensive objects — e.g., a configuration class loaded once per transaction), Strategy (interchangeable algorithm implementations behind a common interface), Decorator (wrap an existing class to add behaviour). Know how to identify which pattern solves a given architectural problem — the exam presents a scenario and asks which pattern is most appropriate.

Testing and Debugging (25%)

Advanced testing: Test isolation with @TestSetup (runs once, shares data across all test methods), Test.loadData() for CSV-based test data. HTTP callout mocking: HttpCalloutMock interface — implement respond() and register with Test.setMock(HttpCalloutMock.class, mock). Testing async Apex: wrap the enqueue call between Test.startTest() and Test.stopTest() — stopTest() forces async execution to run synchronously so you can assert results. Mixed DML errors: cannot insert setup objects (User, Group) and non-setup objects (Account, Contact) in the same transaction — wrap setup DML in a System.runAs() block. Debug log analysis: read EXECUTION_STARTED → SOQL queries (with row counts) → DML statements → EXCEPTION events to diagnose runtime issues.

Integration (23%)

Apex callouts: Http, HttpRequest, HttpResponse for REST; WebServiceCallout.invoke() for SOAP. Cannot make callouts from triggers (they are synchronous DML context) — use a future method or queueable. Named Credentials: store endpoint URL and authentication credentials securely — use callout:NamedCredentialName/path in the endpoint URL. Platform Events: define fields on a Platform Event object, publish with EventBus.publish(), subscribe with triggers or flows. High-volume platform events have at-least-once delivery. Apex REST: expose Apex as a REST API using @RestResource(urlMapping='/v1/myEndpoint/*') and @HttpGet, @HttpPost, etc. annotations.

Performance (17%)

SOQL selectivity: queries are selective when the WHERE clause uses indexed fields (Id, Name, ExternalId, unique fields, or custom indexed fields) and filters enough records (generally <10% of the object's records or <200k records). Non-selective queries on large objects cause timeouts. Query Plan tool: shows whether Salesforce will use an index (low cost) or a full table scan (high cost) for a query. Heap size: 6 MB synchronous / 12 MB async — avoid storing large collections in static variables across transaction boundaries. CPU limit: 10,000 ms synchronous — avoid nested loops over large collections; prefer Maps over repeated list iteration. Async for long-running work: Queueable (chaining, passing complex state), Batch Apex (process millions of records), Scheduled Apex (time-based execution).

Developer Experience (10%)

SFDX / Salesforce CLI: source-driven development using sf project retrieve and sf project deploy. Scratch orgs: temporary, configurable orgs for development and testing — created from a project definition file, last 1–30 days. Unlocked Packages: 2nd-generation packages that are modular, versionable, and source-tracked. Unlike managed packages (ISV), unlocked packages are for org-specific development. Know the difference between 1GP (first-generation, subscriber-opaque), 2GP unlocked (org-internal, source-trackable), and 2GP managed (ISV distribution with namespace). CI/CD: understand the concept of automated pipeline: pull request → scratch org → run tests → deploy to sandbox → promote to production.