aws-architecture-patterns

name	aws-architecture-patterns
description	AWS service selection, well-architected lens, cost patterns

AWS Architecture Patterns

Service Selection Heuristics

Compute

Need	Service	Avoid if
Stateless API / microservice	Lambda (if <15min) or ECS Fargate	Cold starts are unacceptable (Lambda)
Long-running / stateful workload	ECS Fargate or EC2 Auto Scaling	You don't want to manage infra (EC2)
Kubernetes required	EKS	Team has no K8s experience
Batch / data processing	AWS Batch or Lambda + SQS
Background jobs, workers	ECS + SQS
Simple scheduled tasks	EventBridge + Lambda

Rule of thumb: Lambda first → ECS Fargate if Lambda won't fit → EKS only if K8s is a hard requirement.

Database

Need	Service	Notes
Relational, OLTP	RDS Aurora PostgreSQL	Serverless v2 for variable load
Key-value, low latency	DynamoDB	Requires careful access pattern design upfront
Cache / session	ElastiCache (Redis)
Full-text search	OpenSearch	Expensive to run; consider Typesense on EC2
Time-series	Timestream or InfluxDB on EC2
Data warehouse / analytics	Redshift or Athena (if data is in S3)
Graph	Neptune	Niche; only if graph traversal is core

Aurora Serverless v2 is often the right default for new relational workloads — scales to zero on dev, handles spiky production traffic.

Messaging & Queues

Pattern	Service
Task queue, background jobs	SQS (Standard or FIFO)
Fan-out / pub-sub	SNS → SQS
Real-time event streaming	Kinesis Data Streams or MSK (Kafka)
Event bus between services	EventBridge
Websockets / real-time push	API Gateway WebSocket or AppSync Subscriptions

Storage

Need	Service
Object / blob storage	S3
CDN / static assets	CloudFront + S3
Shared filesystem (ECS, EC2)	EFS
Block storage (EC2)	EBS gp3

Cost Patterns

• Egress is the hidden cost. Data leaving AWS (to internet or cross-region) costs ~$0.09/GB. Design to minimize cross-region calls.
• NAT Gateway is expensive at scale (~$0.045/GB processed). Consider VPC endpoints for S3/DynamoDB to avoid it.
• RDS always has at least one standby in Multi-AZ — account for 2x instance costs in production.
• CloudWatch Logs ingestion costs accumulate fast. Set retention policies and filter before sending to Logs.
• Data Transfer Accelerator / Global Accelerator only worth it for latency-sensitive global apps.

Well-Architected Lens Quick Checks

Before finalizing an AWS architecture, ask:

1. Reliability: Is there a Multi-AZ deployment? What's the RTO/RPO?
2. Security: Are all S3 buckets private by default? Is IAM following least privilege? Is data encrypted at rest and in transit?
3. Performance: Are you in the right region for your users? Is caching in place for repeated reads?
4. Cost: Are dev/staging environments using auto-shutdown or Serverless? Are Reserved Instances / Savings Plans applied to stable workloads?
5. Operational Excellence: Is there centralized logging (CloudWatch / OpenSearch)? Are alerts configured on error rates and latency P99?
6. Sustainability: Are idle resources (dev DBs, unused EC2s) scheduled to stop outside business hours?

Common Anti-patterns

• Lambda for everything — Websockets, large file processing, and CPU-heavy tasks are poor fits.
• RDS for high-throughput key-value — Use DynamoDB or ElastiCache instead.
• Single-AZ in production — Never. Even for non-critical apps, the cost delta is small.
• Hardcoded credentials — Always use IAM roles + Secrets Manager.
• Skipping VPC — Even serverless workloads that need RDS access need VPC configuration.