Understanding AWS Lambda: Invocations, Events and How It Really Works

Source: Dev.to

Invocation Models

• Synchronous invocations – request/response style, commonly used with API Gateway
• Asynchronous invocations – event‑driven, retried automatically, great for background jobs
• Event source mappings – Lambda polls services like SQS, DynamoDB Streams, and Kinesis

Each model has very different behavior regarding retries, error handling, concurrency, and cost.

Key Concepts

• How Lambda scales
• When cold starts happen
• How retries actually work

Understanding these points helps you move beyond treating Lambda as “magic” and enables the design of simpler, more resilient systems.

Detailed breakdown with real‑world context (not just docs)