Depends on the kind of application. A typical trading system, cannot rely on auto scaling because by the time system scales up there would be already a lot of failed requests. Better to scale up in advance for such systems. Whereas normal web applications can maybe rely on auto scaling. Above sudden traffic spike is a thundering herd problem, you might have to take call between: 1. Rate limiting request 2. Queuing requests Else if we allow all requests, it has the potential to bring the whole application down.

If my web application is facing sudden traffic spikes, I’d scale resources ahead of time if I know the spike is coming, like during a big live-stream event. I’d also use edge computing to process requests closer to users and lighten the load on central servers. To handle the surge, I’d prioritize traffic for important users or services, premium users for instance, and, if necessary, lower video quality to keep everything running smoothly without crashing the system.

Use Queueing for Overloaded Requests • Implement a message queue (e.g., Azure Service Bus) to handle requests during peak traffic, ensuring they are processed in order even if the system is slow.

Here common idea is same, 1. We have to build the infrastructure that scale app server and service underneath services horizontally. 2. This task has becomes simpler when we our applications on cloud, where we can scale our resources horizontally on demand. 3. However, its matter of cost effect when we choose on demand. 4. We have assess the required capacity upfront with considering best cost saving plan.