serverless-patterns

name	serverless-patterns
description	Lambda, cold starts, event-driven design, API Gateway, and serverless frameworks
metadata	{"author":"cosmicstack-labs","version":"1.0.0","category":"backend","tags":["serverless","lambda","cloud","aws","event-driven"]}

Serverless Patterns

Build scalable serverless applications.

Core Patterns

Function Design

• Single responsibility per function
• Stateless (use external storage for state)
• Idempotent handlers (retry-safe)
• Receive event, process, return/forward

Cold Start Mitigation

Strategy	Effect	Tradeoff
Provisioned Concurrency	Zero cold starts	Cost
Smaller runtime (Node/Python)	Faster start	Language choice
Keep-alive ping	Reduce frequency	Extra cost
Lambda SnapStart (Java)	Fast restore	State constraints
Lambda@Edge	Regional distribution	1MB response limit

Event-Driven Design

Event Types

Events:
  - UserRegistered { userId, email, timestamp }
  - OrderPlaced { orderId, items, total }
  - PaymentProcessed { orderId, amount, status }
  - EmailSent { to, template, variables }

SQS + Lambda Pattern

API Gateway → Lambda (producer) → SQS → Lambda (consumer) → DynamoDB

Benefits: decoupling, buffering, retry, dead-letter queue.

API Gateway Patterns

• Request validation at gateway level
• Caching for GET endpoints (TTL per route)
• WAF for rate limiting and IP blocks
• Custom domain with ACM certificate
• Usage plans for API keys

Frameworks

• SAM (AWS) — YAML/YML, local testing
• Serverless Framework — Multi-cloud, plugins
• CDK (AWS) — Full programming languages
• Terraform — If already using for other infra
• Chalice (Python) — Flask-like, AWS only

Best Practices

• Function timeout: max 30s for APIs, 15min for background
• Memory: allocate more = more CPU (for compute-heavy, use 1.7GB+)
• Monitor: Duration, Invocations, Error count, Throttles
• Logs: structured JSON to CloudWatch
• Security: least-privilege IAM roles per function