19.14Ask about timing

Not:

“Should it be real-time?”

That's too vague.

Ask:

“How long after a customer changes in the source is it acceptable for Salesforce to still show the old value?”

Possible answers:

< 5 seconds

< 5 minutes

same day

overnight

Those answers tell you whether you need:

synchronous API

events/CDC

queue

15-minute scheduler

nightly batch