The picture to memorize

If the interviewer hands you a blank screen and says:

“How would you build a Mule API that puts customers into Salesforce?”

Start drawing:

HTTP Listener
      ↓
Validate
      ↓
Save original request
      ↓
Transform Message
    DataWeave
      ↓
Salesforce
    Upsert
      ↓
Transform Message
      ↓
HTTP Response

Then say:

“I'd use an external customer ID for idempotent Salesforce upserts, keep the public API model decoupled from the Salesforce object model, preserve any input I need later in variables, and add structured error handling and correlation-aware logging.”

That already sounds substantially more like a MuleSoft developer than someone who only tested Mule integrations.

Module 3 is the important one: DataWeave

Next we should spend the largest chunk of Day 1 on DataWeave 2.0. We'll go from simple field mapping to arrays, map, filter, conditional fields, defaults/nulls, flattening/nesting, dates, strings, Salesforce records, and the DataWeave questions you're realistically likely to encounter in an interview.