What it is: An in-memory key-value store with advanced data structures.

What it’s for:

• Caching + sessions + pub/sub + leaderboards.
• More features than Memcached.

Key ideas:

• Supports persistence (optional) and replication in managed setups.
• Common for session store.

Hard words:

• *data structure* /ˈdeɪtə ˈstrʌktʃər/: cấu trúc dữ liệu
• *persistence* /pərˈsɪstəns/: lưu bền (không mất hoàn toàn)
• *replication* /ˌreplɪˈkeɪʃn/: nhân bản/sao chép