17.8Interview answer

A concise version:

“I'd expose an HTTP API, validate the request at the boundary, transform the external customer model into the Salesforce Account model using DataWeave, and use Salesforce Upsert against a unique stable External ID rather than query-then-create. I'd classify permanent versus transient connector errors, use bounded retries only where the operation is idempotent, normalize Salesforce errors into the API contract, and propagate a correlation ID. MUnit would cover mappings, branches, and error behavior, while a smaller integration suite against a Salesforce sandbox would prove the real schema, permissions, and External-ID semantics.”

That's a complete senior answer.