In this chapter we’ll look at how our services will connect to each other while they are deployed across multiple environments.

Let’s quickly review the setup that we’ve created back in the Organizing services chapter.

  1. We have two repos — serverless-stack-demo-ext-resources and serverless-stack-demo-ext-api. One has our infrastructure specific resources, while the other has all our Lambda functions.
  2. The serverless-stack-demo-ext-resources repo is deployed a couple of long lived environments; like dev and prod.
  3. While, the serverless-stack-demo-ext-api will be deployed to a few ephemeral environments (like featureX that is connected to the dev environment), in addition to the long lived environments above.

But before we can deploy to an ephemeral environment like featureX, we need to figure out a way to let our services know which infrastructure environment they need to talk to.

Let’s look at how to do that.

Set a stage environment variable

In the serverless.common.yml file, we defined:

  # Our stage is based on what is passed in when running serverless
  # commands. Or fallsback to what we have set in the provider section.
  stage: ${opt:stage, self:provider.stage}
    prod: prod
    dev: dev
  resourcesStage: ${self:custom.resourcesStages.${self:custom.stage},}

The above code reads the current stage from the serverless commands, and selects the corresponding resourcesStage config.

  • If the stage is prod, it uses the prod infrastructure.
  • If the stage is dev, it uses the dev infrastructure.
  • And if stage is featureX, it falls back to the dev config and uses the dev infrastructure.

And then in each service, we are going to pass the resourcesStage to the Lambda functions as an environment variable. Open up the serverless.yml file in a service.


custom: ${file(../../serverless.common.yml):custom}

    stage: ${self:custom.stage}
    resourcesStage: ${self:custom.resourcesStage}

This adds a resourcesStage environment variable to all the Lambda functions in the service. Recall that we can access this via the process.env.resourcesStage variable at runtime.

Create a stage based config

Now in our config.js, we’ll read the resourcesStage from the environment variable process.env.resourcesStage.

const stage = process.env.stage;
const resourcesStage = process.env.resourcesStage;
const adminPhoneNumber = "+14151234567";

const stageConfigs = {
  dev: {
    stripeKeyName: "/stripeSecretKey/test"
  prod: {
    stripeKeyName: "/stripeSecretKey/live"

const config = stageConfigs[stage] ||;

export default {

Finally, while calling DynamoDB we can use the config to get the DynamoDB table we want to use. In libs/dynamodb-lib.js:

import AWS from "./aws-sdk";
import config from "../config";

const dynamoDb = new AWS.DynamoDB.DocumentClient();

export function call(action, params) {
  // Parameterize table names with stage name
  return dynamoDb[action]({
    TableName: `${config.resourcesStage}-${params.TableName}`

The above setup ensures that even when we create numerous ephemeral environments for our API services, they’ll always connect back to the dev environment of our resources.

Next, let’s look at how to store secrets across our environments.