====== API Gateway ======

**What it is:** A managed service to create, publish, and secure APIs.

**What it’s for:**
  * Build REST/HTTP APIs in front of Lambda, services, or other backends.
  * Add authentication/authorization, throttling, and monitoring.

**Key ideas:**
  * Common integrations:
    * Lambda (serverless APIs)
    * HTTP backends (ALB, EC2, on-prem)
  * Supports features like caching, request validation, and usage plans (high-level).

**Exam cues:**
  * “create an API for Lambda without servers” → API Gateway + Lambda.
  * “rate limit API clients” → API Gateway throttling/usage plans.

**Hard words:**
  * *publish* /ˈpʌblɪʃ/: công bố
  * *backend* /ˈbækend/: hệ phía sau
  * *throttling* /ˈθrɑːtlɪŋ/: giới hạn lưu lượng
  * *validation* /ˌvælɪˈdeɪʃn/: kiểm tra hợp lệ