The Node.js 18 runtime brings the latest and greatest LTS version of Node.js to Lambda, and as of today, it is officially supported in Lumigo!

What's new in the Node.js 18 runtime

Node.js 18 itself brings a built-in test runner, the support for the Fetch API, and a few other quality-of-life improvements. But what makes the Node.js 18 runtime very interesting, is the adoption of the AWS SDK 3 for Javascript: it is a rewrite of the AWS SDK that focuses on first-class Typescript support and modularity.

Extolling the virtues of Typescript's static type system (as opposing to effectively not having static type checks like Javascript), is something that can get me going for a while, and I am sparing everyone it.

But modularity has implications for cold starts. It is a known fact that the size of the Lambda bundle affects cold starts. It is pretty much as the intuition goes: the more code to load into the Node runtime, the longer the startup.

Another nice thing that can speed up your Lambda functions is with AWS SDK 3 is enablement by default of the TCP connection re-use, which can shave significant amounts of time across invocations for Lambda instances that are kept busy.

What do you need to do in Lumigo to use the Node.js 18 runtime?

Just turn on Lumigo autotracing as always. If you went ahead and adopted Node.js 18 a few days ago, and Lumigo told you the runtime is not supported, by now you will have noticed that Lumigo by now has set up autotracing for your Node.js 18 functions that you selected for autotracing in the UI, or using the `lumigo:auto-trace=true` AWS Tag. Nice and easy :-)