Where to properly store AWS credentails for Next.js application deployed on Zeit

I have a Next.js application that is deployed to Zeit. I want to have an access to some of AWS services: SNS to send text messages and DynamoDB to store some data.

There is aws-sdk available for JavaScript so it is pretty easy to utilize any service from AWS

Example function to send text messages

import SNS from 'aws-sdk/clients/sns';

export function sendTextMessage(message, phone) {
  return new Promise((resolve, reject) => {
    const snsParams = {
      Message: message,
      PhoneNumber: phone
    };

    const snsClient = new SNS({ region: 'us-east-1' });

    snsClient.publish(snsParams, (error, data) => {
      if (error) {
        reject(error);
      } else {
        resolve(data);
      }
    });
  });
}

The question is where/how can I safely store AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY on Zeit hosting? So it is not exposed to end users.

Any help is appreciated! Thanks