Mastering AWS for Developers: Key Services Every MERN Stack Engineer Should Know

When it comes to deploying modern applications, Amazon Web Services (AWS) remains the go-to cloud platform. But with 200+ services, it’s easy to feel overwhelmed. As a MERN (MongoDB, Express, React, Node.js) developer preparing for real-world projects or interviews, you don’t need to know everything — just the core AWS services that directly impact application development and deployment.

In this blog, we’ll explore 5 AWS services every developer should master, with examples and use cases tailored for SaaS and MERN stack projects.

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1. Amazon EC2 (Elastic Compute Cloud) – Your Virtual Server

What it is: EC2 provides resizable virtual machines in the cloud.

When to use:

• Running Node.js backend APIs.

• Hosting services that require full server control.

• Running cron jobs or background workers.

Example: Deploying an Express.js backend on an EC2 instance with NGINX + PM2 for process management.

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2. Amazon S3 (Simple Storage Service) – Scalable Object Storage

What it is: Secure and highly scalable object storage service.

When to use:

• Store user-uploaded files (profile pictures, reports, invoices).

• Host static websites (React SPA).

• Store backups and logs.

Code Example (Node.js file upload):

import { S3Client } from '@aws-sdk/client-s3';
import multerS3 from 'multer-s3';
import { configData } from '../config/config';
import path from 'path';

export const s3Client = new S3Client({
    region: 'ap-south-1',
    credentials: {
        accessKeyId: configData.s3accessKeyId,
        secretAccessKey: configData.s3secretAccessKey,
    },
});

export const s3Storage = multerS3({
    s3: s3Client,
    bucket: `${process.env.S3_BUCKETNAME}`,
    metadata: (req, file, cb) => {
        cb(null, { fieldname: file.fieldname });
    },
    key: (req, file, cb) => {

        if (!file || !file.originalname) {
            return cb(new Error('No file provided.'));
        }

        const allowedExtensions = ['.jpg', '.jpeg', '.png'];
        const ext = path.extname(file.originalname).toLowerCase();

        if (!allowedExtensions.includes(ext)) {
            return cb(new Error('Only .jpg, .jpeg, and .png formats are allowed.'));
        }

        const fileName = `Profile-Images/${Date.now()}_${file.fieldname}_${file.originalname}`;
        cb(null, fileName);
    }

});

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3. AWS Lambda – Serverless Functions

What it is: Run code without managing servers.

When to use:

• Event-driven tasks (file upload triggers, email sending).

• Background processing (image compression, PDF generation).

• Low-traffic APIs to save cost.

Example: Triggering a Lambda when a new file is uploaded to S3 → process → save result in MongoDB.

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4. Amazon RDS (Relational Database Service) & DynamoDB

• RDS: Managed SQL databases (MySQL, PostgreSQL).

• DynamoDB: NoSQL key-value store, fully serverless.

When to use:

• Use RDS when you need transactions & complex queries.

• Use DynamoDB for fast lookups, real-time apps, or event-driven workloads.

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5. Amazon CloudWatch & IAM – Monitoring & Security

• CloudWatch: Logs, metrics, alarms for apps.

• IAM (Identity & Access Management): Secure access with least-privilege policies.

Why it matters:

• CloudWatch helps debug production issues (API latency, memory leaks).

• IAM ensures your app isn’t overexposed (e.g., public S3 buckets = security nightmare).

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Quick Deployment Example: MERN App on AWS

1. React frontend → Deploy on S3 + CloudFront.

2. Node.js backend → Run on EC2 or Elastic Beanstalk.

3. MongoDB → Use MongoDB Atlas on AWS (or DynamoDB if allowed).

4. File uploads → Store on S3.

5. Monitoring → Use CloudWatch for logs + alerts.