9 Serverless Functions

Serverless architectures, where you deploy functions that are fully managed by a Cloud environment and are executed in ephemeral processes, require a unique approach.

Traditional frameworks like Grails and Spring are not really suitable since low memory consumption and fast startup time are critical, since the Function as a Service (FaaS) server typically spins up your function for a period using a cold start and then keeps it warm.

Micronaut’s compile-time approach, fast startup time, and low memory footprint make it a great candidate for developing functions, and Micronaut includes dedicated support for developing and deploying functions to AWS Lambda, Google Cloud Function, Azure Function, and any FaaS system that supports running functions as containers (such as OpenFaaS, Rift or Fn).

There are generally two approaches to writing functions with Micronaut:

1. Low-level functions written using the native API of the function platform

2. Higher-level functions where you simply define controllers as you normally do in a typical Micronaut application and deploy to the function platform.

The first has marginally less startup time overhead and is typically used for non-HTTP functions such as functions that listen to an event or background functions.

The second is only for HTTP functions and is useful for users who want to take a slice of an existing application and deploy it as a serverless function. If cold start performance is a concern it is recommended that you consider building a native image with GraalVM for this option.