High traffic sites require dedicated hosting solutions that are tailored to their particular software stack, in your case WordPress PHP.
Beyond software specific optimization, unexpected traffic coming in to a website means the server will be under a lot of stress, which may result in memory leaks or the force shutdown of a process that the CPU is unable to handle.
To fix this, hosting providers use something called load balancers. Once a load balancer sees your server starting to sweat, it opens up a carbon copy secondary server and splits the traffic in two, monitoring both servers until it needs to open or close another round of servers. Servers can also be configured to automatically move to more powerful hardware based on incoming traffic, the result is similar.
Going a step further, some websites might have a service level agreement (SLA) that states “Keep my site live 99.5% of the time or host my site for free, you choose.” They pay premium rates for blanket protection since enterprise level rollouts require a lot of specialized maintenance. For special services you may get in touch to a2a Business Link