Perfect is the enemy of good. (Start simple, optimize later)
Building full-stack apps on AWS? Here are three patterns to use, with commentary about when each makes sense.
Pattern 1: Go Serverless
This is Lambda + API Gateway + S3, with your frontend on CloudFront and your API as Lambda functions. Database is either RDS Aurora Serverless (SQL) or DynamoDB (NoSQL).
When it works: Perfect for MVPs or apps with unpredictable traffic. You literally pay nothing when no one's using it.
The catch: Cold starts. First request after idle time can take 1-2 seconds. If that's a dealbreaker, look at Pattern 2.
Pattern 2: Containers on ECS Fargate
Your app runs in Docker containers without managing servers. It's like having a traditional server, but without handling infrastructure.
When it works: You need consistent performance, WebSocket connections, or you're running something that doesn't fit the Lambda model well (such as long-running processes).
The catch: Costs more upfront. You're paying $30-50/month minimum even with zero traffic. But performance is solid.
Pattern 3: Mix and Match
Use serverless for simple stuff, containers for complex operations. This seems like what most production apps end up doing.
For example, in an image-sharing app: Lambda handles authentication and simple CRUD operations, S3 events trigger Lambda for image processing, and WebSocket servers run on ECS for real-time features.
Things That Actually Matter
Keep your database private. RDS should be in private subnets, accessed only by your Lambda functions or ECS tasks in the same VPC. Use RDS Proxy if you're hitting connection limits with Lambda.
Put CloudFront in front of everything. Seriously, everything. It'll cut your origin requests by 80% with proper cache headers.
Start simple. Pattern 1 costs about $10/month for low traffic and scales to millions of users. You can always evolve later based on actual bottlenecks.
The serverless pattern gets expensive above 10M requests/month, but by then you'll have real revenue (hopefully) and data showing you exactly where to optimize. Cross that bridge when you get there.