About a year ago I kept hearing about serverless as the way to go for all new code. It seemed every conference, every cloud vendor, even many developers were discussing serverless as a technique for running small snippets of code. The technology seemed to burn very bright, but then dropped out of the media somewhat. It's still being adopted, but seems less popular than a year ago, with containers and Kubernetes becoming more popular this year.
Serverless computing is kind of a backend-as-a-service (BaaS) or a function-as-a-service (FaaS) architecture where you write and deploy functions on a cloud service that are called by your application as small chunks of functionality. The pricing is by the execution, with a very low cost for resources. Azure Functions cost US$0.20/million calls and US$0.000016 / GB-s. Strange metrics, but the result is a very low cost for most clients to use a functional part of a system. The key is that there are not infrastructure worries. The serverless platform provides the CPU and RAM needed to execute a function, with storage also available on the cloud provider's platform.
I ran across an interesting article that talks about serverless platforms on premises don't quite make sense. The idea with serverless is that you most closely pay for what you use, not being charged for times when your code isn't being executed. On premises, you would need some hardware running all the time that you are paying for, which is ready for when code is called to execute.
I'd disagree slightly, especially with architectures like Azure Stack that blur the line between private and public cloud resources. With Azure Stack, you should (at some point) be able to write applications using serverless functions that execute in your data center. If you need more resources, you scale your data center up with Azure cloud resources, and pay for your usage. When the workload shrinks, you stop using cloud resources and just use your data center.
Most of us won't necessarily want to run an Azure Stack, so why would be use serverless on premises? To me there is one element of a cloud service I can't control: what other people do on the platform. Cloud services are large and distributed and in use by lots of customers at a time. If I execute things in my data center, on some serverless platform, I have better control over how things work and likely more predictable performance. If my workload is well known, I also probably have lower costs.
In many cases, we know the workloads of our databases, and we want predictable performance (however good or bad it is). Databases are potentially a good fit in the cloud, but often in a mature application, we would be better served by keeping the database on premises, especially if we've already invested in the hardware and other resources.
Serverless is a very interesting idea, as is much of the cloud. It might suit your application, or it may not, but you have to think about the requirements for your situation. Knowledge of new options and technology is important for us to intelligently debate and discuss what works best for our organizations.