====== RDS Read Replica ======

**What it is:** An asynchronous copy of a database used primarily for scaling reads.

**What it’s for:**
  * Offload read traffic (reporting, dashboards, read-heavy workloads).
  * Improve performance for read operations.

**Key ideas:**
  * Replication is **asynchronous** (replica may lag behind).
  * Read replicas have their own endpoint.
  * Some engines allow promotion to standalone DB (disaster recovery pattern, but not “automatic same endpoint” like Multi-AZ).

**Exam cues:**
  * “read-heavy workload, scale reads” → Read Replica.
  * “replica lag is acceptable” → asynchronous replica.

**Hard words:**
  * *asynchronous* /eɪˈsɪŋkrənəs/: bất đồng bộ
  * *lag* /læɡ/: độ trễ (chậm hơn dữ liệu gốc)
  * *promote* /prəˈmoʊt/: nâng cấp (thành primary)