Native Mode vs Datastore Mode

Step 1:Set Firestore to Datastore Mode

1. Go to the Google Cloud Console.

2. Select your project.

3. In the left nav, go to Firestore → Create Database.

4. Choose Datastore mode, select a location (cannot be changed later), and create it.

Step 2: Create Your Node.js GAE App

File structure example:

my-app/
├── package.json
├── app.js
└── app.yaml

             

Step 3: Add Firestore SDK

In your project folder, run:

npm install @google-cloud/datastore

             

Step 4: Initialize Firestore in app.js & use it (here saving)

>>>NOTE: credentials and permission is setup in console --see at the bottom of this page

const express = require('express');
const { Datastore } = require('@google-cloud/datastore');

const app = express();

// Creates a Datastore client using Application Default Credentials
const datastore = new Datastore();

app.get('/', async (req, res) => {
  const kind = 'Message';
  const taskKey = datastore.key([kind]);

  const entity = {
    key: taskKey,
    data: {
      text: 'Hello from GAE and Firestore in Datastore Mode!',
      timestamp: new Date(),
    },
  };

  try {
    // Save the entity
    await datastore.save(entity);

    // Query latest 5 messages
    const query = datastore
      .createQuery(kind)
      .order('timestamp', { descending: true })
      .limit(5);

    const [messages] = await datastore.runQuery(query);

    res.send(messages);
  } catch (error) {
    console.error('Datastore error:', error);
    res.status(500).send('Error accessing Datastore');
  }
});

const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`App listening on port ${PORT}`);
});

Code Snippet to read/retrieve from Datastore

const { Datastore } = require('@google-cloud/datastore');

// Initialize Datastore client (uses Application Default Credentials on GAE)
const datastore = new Datastore();

// Function to retrieve latest messages
async function getLatestMessages(limit = 5) {
  const query = datastore
    .createQuery('Message')
    .order('timestamp', { descending: true })
    .limit(limit);

  try {
    const [messages] = await datastore.runQuery(query);
    return messages;
  } catch (error) {
    console.error('Error retrieving messages from Datastore:', error);
    throw error;
  }
}

Step 5: Create app.yaml for GAE Standard

runtime: nodejs20  # or nodejs18
instance_class: F1

env_variables:
  GOOGLE_NODE_RUNFILES: "1"

note:

instance_class: F1

This controls the size and cost of each App Engine instance. It's optional, but important if you want to manage performance and billing.

• F1 is the smallest, cheapest, and free-tier eligible (ideal for testing or small traffic).

What is GOOGLE_NODE_RUNFILES: "1"?

This is a special GAE setting used with Node.js apps. It tells App Engine to include node_modules binaries and runtime files when packaging your app.

• It’s helpful for compatibility and ensures that dependencies (especially those that rely on compiled binaries like firebase-admin) run properly.

• Without this, certain modules may behave unexpectedly in some edge cases.

You usually don’t need to touch this unless troubleshooting issues — but including it is safe and ensures maximum compatibility.

Step 6: Deploy to GAE

Make sure you're authenticated with Google Cloud SDK:

gcloud auth login
gcloud config set project [YOUR_PROJECT_ID]  
gcloud app deploy  

Visit your app after deployment:

gcloud app browse  

Step 7 – Verify IAM Permissions

By default, GAE uses this service account:

[PROJECT_ID]@appspot.gserviceaccount.com

Make sure it has at least the Cloud Datastore User role:

1. Go to IAM & Admin.

2. Find the default App Engine service account.

3. Ensure it has one of these roles:

   • Cloud Datastore User (recommended)

   • Editor (for full access during development)

NOTE:

What Does await Do in JavaScript?

await is a keyword in JavaScript that can only be used inside an async function. It tells the program to wait for a Promise to complete before continuing.

const result = await someAsyncFunction();

• someAsyncFunction() returns a Promise.

• await pauses execution of the current async function until the Promise is resolved (success) or rejected (error).

• The resolved value gets stored in result.

• If the Promise is rejected, the error can be caught using try...catch.