What it is: Rules that automatically transition objects between storage classes or expire/delete them.

What it’s for:

• Reduce cost (move old data to cheaper storage).
• Automatically delete data after a retention period.

Key ideas:

• Can transition: Standard → IA → Glacier, etc.
• Can expire current versions and noncurrent versions (when versioning is on).

Exam cues:

• “move logs to Glacier after 90 days” → lifecycle transition.
• “delete files after 1 year” → lifecycle expiration.

Hard words:

• *transition* /trænˈzɪʃn/: chuyển đổi
• *expire* /ɪkˈspaɪər/: hết hạn
• *retention* /rɪˈtenʃn/: thời gian lưu giữ