Your service handles today's traffic comfortably. Marketing says 10x is coming in six weeks. What do you do?
Answer it out loud before you open anything. The value of the flags below is in comparing them to what you actually said.
The situation behind the question
A single service behind a load balancer, two instances, one Postgres primary, one Redis, one queue with three workers. Nothing is currently on fire.
What it is really testing
Whether the candidate scales the constraint or scales everything. The interesting answer identifies which resource saturates first and says how they would know, rather than reciting a list of scaling techniques.