React Native应用AWS Cognito/Amplify认证配置及Amplify定价咨询

Hey there! Let's tackle your three questions clearly and practically— I’ve worked with both Cognito and Amplify in React Native projects, so I’ll share what I know to get you sorted.

1. Standard Flow to Configure AWS Cognito in React Native #

If you want to use Cognito directly without Amplify, follow this step-by-step process:

Step 1: Install Required Dependencies #

Start by adding the official Cognito SDK and a network info package (to handle offline scenarios):

npm install amazon-cognito-identity-js @react-native-community/netinfo
# Or with yarn
yarn add amazon-cognito-identity-js @react-native-community/netinfo

Step 2: Set Up Cognito Resources in AWS Console #

• Head to the AWS Cognito Console, create a User Pool with your preferred settings (password policies, MFA requirements, etc.).
• Create an App Client inside the user pool—make sure to disable "Generate client secret" (React Native is a public client, so secrets aren’t secure here).
• Note down your UserPoolId, ClientId, and the AWS region where your pool is hosted.

Step 3: Initialize Cognito in Your App #

Create a utility file (like cognitoConfig.js) to store your config and initialize the user pool:

import { CognitoUserPool } from 'amazon-cognito-identity-js';

const poolData = {
  UserPoolId: 'YOUR_USER_POOL_ID',
  ClientId: 'YOUR_APP_CLIENT_ID',
};

export const userPool = new CognitoUserPool(poolData);

Step 4: Implement Core Authentication Functions #

Here are examples for common actions you’ll need:

• User Registration:

  import { CognitoUserAttribute } from 'amazon-cognito-identity-js';
  import { userPool } from './cognitoConfig';
  
  const signUp = async (email, password) => {
    const attributeList = [
      new CognitoUserAttribute({ Name: 'email', Value: email }),
    ];
  
    return new Promise((resolve, reject) => {
      userPool.signUp(email, password, attributeList, null, (err, result) => {
        if (err) reject(err);
        else resolve(result.user);
      });
    });
  };
  

• User Login:

  import { CognitoUser, AuthenticationDetails } from 'amazon-cognito-identity-js';
  import { userPool } from './cognitoConfig';
  
  const signIn = async (email, password) => {
    const authenticationDetails = new AuthenticationDetails({
      Username: email,
      Password: password,
    });
  
    const cognitoUser = new CognitoUser({
      Username: email,
      Pool: userPool,
    });
  
    return new Promise((resolve, reject) => {
      cognitoUser.authenticateUser(authenticationDetails, {
        onSuccess: (session) => resolve(session),
        onFailure: (err) => reject(err),
      });
    });
  };
  

• Fetch Current User Session:

  import { userPool } from './cognitoConfig';
  
  const getCurrentSession = async () => {
    const cognitoUser = userPool.getCurrentUser();
    if (!cognitoUser) return null;
  
    return new Promise((resolve, reject) => {
      cognitoUser.getSession((err, session) => {
        if (err) reject(err);
        else resolve(session);
      });
    });
  };
  

2. Configure AWS Amplify with Only Required Features #

If you opt for Amplify but want to cut out unused features, here’s how to do it cleanly:

Step 1: Install Amplify CLI and Core Packages #

First, set up the CLI and install only the modules you need:

# Install Amplify CLI globally
npm install -g @aws-amplify/cli
# Install core and required modules in your app
npm install aws-amplify @aws-amplify/ui-react-native @aws-amplify/datastore

Step 2: Initialize Amplify and Add Only Needed Categories #

Run amplify init in your project root, follow the prompts to connect your AWS account. Then add only the features you want:

# Add Authentication (includes user management via Cognito)
amplify add auth
# Add Storage (S3 integration)
amplify add storage
# Add DataStore (local + cloud sync via AppSync/DynamoDB)
amplify add api # Choose "GraphQL" when prompted, then select "DataStore" as the use case

Step 3: Remove Unwanted Features (If Accidentally Added) #

If you added extra categories by mistake, you can remove them:

amplify remove <category-name> # e.g., amplify remove analytics

Step 4: Configure Amplify in Your App #

In your root component (like App.js), initialize Amplify with only the necessary imports:

import Amplify from 'aws-amplify';
import config from './src/aws-exports';
import { Auth, Storage, DataStore } from 'aws-amplify';

// Initialize only the features you need
Amplify.configure(config);

// Now you can use Auth, Storage, DataStore directly
// Example: Auth.signIn(email, password)

Important Note #

The auto-generated aws-exports.js file will only include config for the categories you added, so you won’t have redundant code for unused features.

3. Detailed AWS Amplify Pricing Rules #

Amplify doesn’t charge extra fees—its cost is tied directly to the underlying AWS services it uses. Here’s a breakdown of the key costs:

Authentication (Cognito) #

• Monthly Active Users (MAU): First 5,000 MAUs per month are free. Beyond that, it’s $0.005 per MAU/month.
• Authentication Requests:
  • First 1 million requests per month are free.
  • $0.015 per 1,000 requests after that.
• MFA & Advanced Security:
  • SMS MFA: $0.0065 per message + carrier fees.
  • TOTP MFA: Included in MAU pricing (no extra cost).
  • Advanced Security (risk-based auth): $0.001 per MAU/month (after free tier).

Storage (S3) #

• Storage Capacity: First 5GB of standard storage is free per month. Beyond that, $0.023 per GB/month (cheaper tiers like Glacier are available for long-term storage).
• Requests:
  • First 20,000 PUT/COPY/POST/LIST requests free; $0.005 per 1,000 after.
  • First 100,000 GET requests free; $0.0004 per 1,000 after.
• Data Transfer: Inbound transfer is free. Outbound to the internet: first 100GB/month free, then $0.09 per GB for the next 400GB, etc.

DataStore #

• Local Storage: 100% free (uses SQLite on the device).
• Cloud Sync (AppSync + DynamoDB):
  • AppSync: First 1 million queries/mutations/subscriptions per month are free. Beyond that, $4.00 per million queries/mutations, $2.00 per million subscriptions.
  • DynamoDB: First 25GB of storage, 2.5 million read capacity units (RCUs), and 2.5 million write capacity units (WCUs) are free per month. Beyond that, pay per RCU/WCU and storage used.

Amplify Console (If Used for Hosting) #

• Build Minutes: First 1,000 minutes per month are free. Beyond that, $0.01 per minute.
• Bandwidth: First 15GB/month free, then $0.15 per GB.

Key Takeaway #

Amplify’s cost scales with your usage of underlying services. For small to medium apps, the free tiers usually cover most needs. To stay cost-conscious, monitor usage via AWS Cost Explorer to avoid unexpected charges.

内容的提问来源于stack exchange，提问作者co_ssm