AWS for Web Applications: A Practical Guide

AWS offers hundreds of services, which creates decision paralysis for developers building web applications. This guide cuts through the noise to explain which services you actually need and how to use them effectively.

Choosing the Right Compute Option

AWS provides multiple ways to run your code. Each fits different use cases:

EC2 (Elastic Compute Cloud): Virtual machines you fully control. Best when you need specific software configurations or persistent processes. You manage the OS, security patches, and scaling.

ECS (Elastic Container Service): Run Docker containers without managing servers (with Fargate) or on EC2 instances you control. Good for containerized applications.

Lambda: Functions that run in response to events. No servers to manage. Best for APIs with variable traffic, event processing, or scheduled tasks. You pay only for execution time.

For most web applications starting out, Lambda with API Gateway or a simple ECS Fargate setup provides the best balance of simplicity and scalability. Migrate to EC2 when you need more control or have predictable high traffic that makes reserved instances cost-effective.

Database Options

RDS (Relational Database Service): Managed PostgreSQL, MySQL, or MariaDB. Handles backups, patching, and replication. Start here for traditional relational data.

RDS sizing tip: Start with the smallest instance that handles your load.
You can scale up with minimal downtime.

Aurora: AWS's cloud-native relational database. More expensive than RDS but offers better performance and automatic scaling. Consider it when you outgrow standard RDS.

DynamoDB: NoSQL key-value and document database. Infinitely scalable, millisecond performance. Best for high-throughput scenarios with known access patterns. Don't use it just because it's serverless;the data modeling is very different from SQL.

ElastiCache: Managed Redis or Memcached. Use for session storage, caching database queries, or rate limiting.

Storage with S3

S3 (Simple Storage Service) stores files reliably and cheaply. Use it for:

• User uploads (images, documents)
• Static assets (CSS, JavaScript)
• Backups and logs
• Data for analytics

Basic S3 patterns:

// Upload a file
const command = new PutObjectCommand({
  Bucket: 'my-bucket',
  Key: 'uploads/image.jpg',
  Body: fileBuffer,
  ContentType: 'image/jpeg'
});
await s3Client.send(command);

// Generate a presigned URL for direct upload
const command = new PutObjectCommand({
  Bucket: 'my-bucket',
  Key: 'uploads/user-file.pdf'
});
const url = await getSignedUrl(s3Client, command, { expiresIn: 3600 });

Presigned URLs let users upload directly to S3, keeping large files off your servers.

CloudFront for CDN

CloudFront is AWS's content delivery network. It caches content at edge locations worldwide, reducing latency for global users.

Common CloudFront configurations:

Static site hosting: Point CloudFront at an S3 bucket containing your built frontend.

API caching: Cache API responses at the edge to reduce origin load.

Dynamic content acceleration: Even for non-cacheable content, CloudFront's global network can reduce latency.

Always put CloudFront in front of S3 buckets. It's faster, cheaper (reduced S3 request costs), and more secure (you can keep S3 buckets private).

Load Balancing and Auto-Scaling

Application Load Balancer (ALB): Routes HTTP/HTTPS traffic to targets (EC2 instances, containers, Lambda functions). Supports path-based routing, host-based routing, and WebSockets.

Auto Scaling: Automatically adjusts capacity based on demand. Configure scaling policies based on CPU utilization, request count, or custom metrics.

For ECS Fargate, enable auto-scaling on the service.
For Lambda, scaling is automatic;no configuration needed.

Cost Optimization Strategies

AWS bills can surprise you. Control costs proactively:

Use the right instance size: Don't over-provision. Monitor utilization and right-size regularly.

Reserved Instances and Savings Plans: Commit to 1-3 years of usage for significant discounts on steady-state workloads.

Spot Instances: Use for fault-tolerant workloads at 60-90% discount. Not suitable for production web servers.

S3 lifecycle policies: Automatically move old data to cheaper storage classes or delete it.

Cost allocation tags: Tag resources by project, environment, or team. Use Cost Explorer to understand where money goes.

Set billing alerts: Configure CloudWatch alarms to notify you when spending exceeds thresholds.

Security with IAM and VPC

IAM (Identity and Access Management): Controls who can do what in your AWS account.

Principles:

• Create individual IAM users, not shared accounts
• Use roles for applications, not access keys
• Follow least privilege;grant only necessary permissions
• Enable MFA for all human users

VPC (Virtual Private Cloud): Your isolated network in AWS.

Best practices:

• Put databases and internal services in private subnets
• Use public subnets only for load balancers and bastion hosts
• Configure security groups as allowlists (deny by default)
• Use VPC Flow Logs for network monitoring

Monitoring with CloudWatch

CloudWatch collects metrics, logs, and traces from AWS resources.

Essential metrics to monitor:

• CPU and memory utilization
• Request counts and latency
• Error rates (4xx and 5xx responses)
• Database connections and query time

CloudWatch Alarms: Notify you when metrics cross thresholds. At minimum, alert on:

• High error rates
• High latency
• Low disk space
• Certificate expiration

CloudWatch Logs: Centralize application logs. Use Log Insights to query across log groups:

fields @timestamp, @message
| filter @message like /ERROR/
| sort @timestamp desc
| limit 100

Getting Started Architecture

For a typical web application, start with:

1. Frontend: S3 + CloudFront for static assets
2. API: Lambda + API Gateway or ECS Fargate
3. Database: RDS PostgreSQL
4. Cache: ElastiCache Redis (if needed)
5. Storage: S3 for uploads
6. Monitoring: CloudWatch metrics, logs, and alarms

This architecture scales from prototype to significant traffic. You can run it for under $100/month in development and scale to handle millions of requests.

Conclusion

AWS is powerful but complex. Start with managed services (Lambda, RDS, S3) that handle operational overhead for you. Add complexity only when you have specific requirements that demand it.

Monitor costs from day one, use IAM roles properly, and put everything in a VPC. These fundamentals will serve you well as your application grows.