====== Partition Key ======

**What it is:** The primary key attribute that determines how data is distributed across partitions.

**What it’s for:**
  * Fast lookup and scalable distribution.

**Key ideas:**
  * Items with the same partition key are stored together.
  * Choosing a good partition key prevents “hot partitions”.

**Exam cues:**
  * “uneven traffic causes throttling” → hot partition; redesign partition key.

**Hard words:**
  * *partition* /pɑːrˈtɪʃn/: phân vùng
  * *distributed* /dɪˈstrɪbjətɪd/: phân tán
  * *throttling* /ˈθrɑːtlɪŋ/: bóp lưu lượng/giới hạn
  * *hot partition* /hɑːt pɑːrˈtɪʃn/: phân vùng bị “nóng” (quá tải)