====== Lambda Concurrency ======

**What it is:** The number of Lambda executions running at the same time.

**What it’s for:**
  * Control scaling and protect downstream systems (DB/APIs).
  * Guarantee capacity for critical functions (reserved concurrency).

**Key ideas (exam-friendly):**
  * **Reserved concurrency**: sets aside capacity for one function and also limits its max concurrency.
  * If concurrency limit is reached, requests can be throttled.

**Exam cues:**
  * “prevent Lambda from overwhelming database” → set reserved concurrency.
  * “guarantee this function always has capacity” → reserved concurrency.

**Hard words:**
  * *concurrency* /kənˈkɝːənsi/: chạy song song
  * *throttled* /ˈθrɑːtld/: bị giới hạn/bóp lưu lượng
  * *downstream* /ˌdaʊnˈstriːm/: hệ phía sau (DB/service nhận tải)