How does an AWS Lambda function scale inside a VPC subnet?

Question

I understand the AWS Lambda is a serverless concept wherein a piece of code can be triggered on some event.
I want to understand how does the Lambda handle scaling?
For eg. if my Lambda function sits inside a VPC subnet as it wants to access VPC resources, and that the subnet has a CIDR of 192.168.1.0/24, which would result in 251 available IPs after subtracting the AWS reserved 5 IPs

Would that mean if my AWS Lambda function gets 252 invocations at the exact same time,
Only 251 of the requests would be served and 1 would either timeout or will get executed once one of the 252 functions completes execution?
Does the Subnet size matter for the AWS Lambda scaling?

I am following this reference doc which mentions concurrent execution limits per region,
Can I assume that irrespective of whether an AWS Lambda function is No VPC or if it's inside a VPC subnet, it will scale as per mentioned limits in the doc?

Answer 1

Vladyslav's answer is still technically correct (Subnet size does matter), but things have changed significantly since it was written and subnet size is much less of a consideration. See aws' announcement:

• Because the network interfaces are shared across execution environments, typically only a handful of network interfaces are required per function. Every unique security group:subnet combination across functions in your account requires a distinct network interface. If a combination is shared across multiple functions in your account, we reuse the same network interface across functions.
• Your function scaling is no longer directly tied to the number of network interfaces and Hyperplane ENIs can scale to support large numbers of concurrent function executions