There are a few ways you can write lambdas. The easiest is using what we call a "magic lambda function" where you just write the code and it looks something like this:

import * as aws from "@pulumi/aws";

const queue = new aws.sqs.Queue("my-queue");

queue.onEvent("handler", (e) => {
    console.log(e);
});

That link above will show you other ways you can write lambdas, some (like my example) you don't get many config options (like memory) but scroll down and there are some good examples there

or maybe that's not Mati's question 🙂