====== Lambda Triggers ======

**What it is:** Event sources that invoke (call) a Lambda function.

**What it’s for:**
  * Automatically run code when something happens in AWS.

**Common triggers (exam staples):**
  * S3 events (ObjectCreated)
  * DynamoDB Streams
  * API Gateway requests
  * EventBridge schedules/rules
  * SQS messages / SNS notifications

**Key ideas:**
  * A trigger defines **when** Lambda runs.
  * Some triggers push events to Lambda; others Lambda polls (e.g., SQS) (conceptually).

**Exam cues:**
  * “process each message from queue” → SQS trigger.
  * “run every hour” → schedule trigger (EventBridge).

**Hard words:**
  * *invoke* /ɪnˈvoʊk/: gọi chạy (hàm)
  * *event source* /ɪˈvent sɔːrs/: nguồn sự kiện
  * *poll* /poʊl/: thăm dò (hỏi định kỳ)