Lambda function times out calling a Step Function (or any other AWS service)

Question

I have an AWS Lambda function that is supposed to call a Step Function via the aws-sdk/client-sfn package. But the function stops and times out at await client.send( command ). What do I need to consider to make it work?

import { SFNClient, StartExecutionCommand } from "@aws-sdk/client-sfn";
const client = new SFNClient({region: "eu-west-1"});

export const handler = async ( event ) => {
    const d = new Date();
    const yr = d.getFullYear();
    const inputParams = {
        "uid": "xxxx-xxxx-xxxx-xxxx",
        "httpMethod": "PUT",
        "settings": 1,
        yr,
        "id": 82,
        "rd": 1
    };        
    const command = new StartExecutionCommand({
        input: JSON.stringify( inputParams ),
        name: "test",
        stateMachineArn: process.env.stateMachine
    });
    try {
        const res = await client.send( command );
        console.log( res );
        client.destroy();
    } catch (error) {
        console.log(JSON.stringify(error));
    }
    return res;
};

The same happens with any other AWS service I am trying to call from this Lambda function. The IAM role has full access to all releant services:

I also set up a VPC endpoint:

The Step Function can be executed manually with no errors.

Answer 1

Solved it by allowing the VPC traffic from the Lambda function's security group.