Core Architecture Principles of Lambda

Lambda is not just a function runner. It is a building block in distributed systems.

Stateless Execution

Each Lambda invocation should be stateless. You cannot rely on in-memory state between executions.

Architecturally, this means:

• Use external storage (DynamoDB, S3, RDS).
• Avoid session memory.
• Design idempotent handlers.

Event-Driven Architecture

Lambda works best in event-driven systems:

• API Gateway → Lambda → Database
• S3 → Lambda → Processing
• SQS → Lambda → Worker logic

This promotes loose coupling.

Fine-Grained Microservices

Because Lambda functions are lightweight and isolated, you can:

• Separate business logic per domain.
• Deploy independently.
• Reduce blast radius of failures.

Concurrency Model

Lambda scales automatically by increasing concurrent executions.

Important limits:

• Account-level concurrency
• Reserved concurrency per function

Architecturally, you must design downstream systems (databases, APIs) to handle scaling.

Architecture Principles

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Should Lambda functions store persistent state in memory?

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Lambda functions must be statelessEvent-driven architecture is centralConcurrency is automatic but must be controlledLambda enables fine-grained microservices