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)