I've inherited an high rps API built with api gateway + lambda + dynamodb and I've found easier and way cheaper to move the thing on ec2. Less headaches too. Resources can be managed more efficiently, cold starts are not a thing, you have predictable latencies, it does serve way more concurrent requests at a fraction of the cost. I go for lambda when i need a service that can scale down, but not when i need to scale up efficiently. Debugging is easier, connection pooling is not an accident, processes' limits and isolation can be managed anyway.