Choosing the Right Async Tool

1. Does it need to run on a recurring schedule? → Scheduled Apex (often paired with Batch or Queueable inside it).
2. Does it need to process a genuinely large number of records — more than a single transaction could reasonably handle? → Batch Apex.
3. Does it need complex parameters (an sObject, a List, a custom class) or job chaining? → Queueable.
4. Otherwise — a simple, one-off async task with only primitive parameters? → @future, the simplest option.

• "Sync a single Account to an external CRM after it\'s updated in a trigger." → @future (simple, primitive Id parameter, one-off).
• "Recalculate a rollup across every Account in the org, nightly." → Scheduled Apex calling Batch Apex (recurring + large volume).
• "Process a List of Opportunities passed from a Visualforce/LWC action, then notify a second system." → Queueable (complex parameter, chaining).
• "Update every Contact\'s mailing address format, a one-time cleanup of 2 million records." → Batch Apex (a genuinely massive one-time volume, no recurrence needed).

This is genuinely the same kind of decision as Module 16's List/Set/Map choice and Module 29's custom setting/metadata/object choice — a short, ordered set of questions, answered by what the actual requirement needs (recurrence, scale, parameter complexity), not by habit or whichever tool happens to be top of mind. Recognizing this recurring decision-making shape is itself a transferable skill, useful well beyond just this specific set of four tools.