Platform architecture; Apex (bulkification, asynchronous patterns, governor limits); Lightning Web Components; Flow and declarative automation; Platform Events; Salesforce APIs (REST, SOAP, Bulk, Streaming, Composite); security and sharing model; data modeling and governance; Visualforce and Aura (legacy maintenance). REST and SOAP APIs; event-driven architecture and Change Data Capture; MuleSoft or comparable middleware/ESB; messaging platforms (Kafka, JMS, Azure Service Bus); API management and gateway patterns; authentication (OAuth 2.0, JWT, SAML, mutual TLS); error handling, retry, and reconciliation design.