When is it not appropriate to use serverless technology such as AWS Lambda? With serverless computing using AWS lambda, Amazon(AWS) is taking the ownership of architecture, administration &amp; deployment aspect of AWS services(VPC/EC2/ELB/AScaling/Rtables/SGroups/etc...) for the application to run. 

With this approach, AWS user losing control on designing an optimal VPC architecture that fine tunes with application

So, when not to think about serverless computing?
There is likely no general answer to this question, but some reasons to not consider Lambda (or other serverless platforms) include:


App requires a language which is not available (C++, Haskell, Erlang, etc.)
Organization has existing substantial investment in containerized (or other) app development model, including developer knowledge, build and deployment pipelines
Portability is concern; i.e. the organization wants/needs to keep app in a state which is portable across platforms (AWS, Azure, various k8s implementations, and so on).
Cost. Do costs of running the Lambda function(s), as well as associated resources (API Gateway, VPC components) exceed budget? This is unlikely if the org. is already running in AWS, but can be a factor when compared against existing (and paid-off) on-premise resources.