In practice
It is a hosting plan problem, not a code problem. Move heavy assets to a CDN and review the plan before the next campaign.
Check what is consuming the bandwidth — uncompressed media and hotlinked images are the usual answer.
Why it matters
The site goes down at exactly the moment traffic is highest, which is usually a campaign or a press hit.
It is entirely predictable from monthly usage, which makes it an avoidable outage.
Related terms