Serverless model as implemented in aws lambda is not faster or cheaper. A single node.js process with fastify.js or hapi.js can handle hundreds if not thousands of requests per second. In lambda to handle 1000 requests per second, assuming a single request take 100ms you need to have 100 instances of lambdas running. Serverless is only cheaper if your application see very little traffic and somehow fit in very limited feature set of lambda. Otherwise, you still need to pay extra for provisioned concurrency and spend engineering resources to workaround lambda limitations.

What often happen is people build own framework on top of serverless instead of just using Rails, Django, Phoenix etc.