Redesigning for a Sustained 10x Traffic Spike

Marketing is planning a 48-hour global promotional event expected to drive roughly 10x normal peak traffic (not the 1.6x campaign spike already assumed in the base design) — closer to 700,000 events/sec at the highest point. This is known two weeks in advance.

1. Walk through which components of the pipeline (from Step 1's math through Step 9's monitoring) would be under-provisioned for this, and by roughly how much.
2. Propose a concrete capacity plan for the 48-hour window, including what you'd change ahead of time versus what you'd rely on autoscaling to handle in the moment.
3. What would you deliberately choose not to scale up, and why is leaving it alone the correct call rather than an oversight?