> For the complete documentation index, see [llms.txt](https://liuzhenglaichn.gitbook.io/system-design/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuzhenglaichn.gitbook.io/system-design/basics/redundancy-and-replication.md).

# Redundancy and Replication

Master-slave replication

Dynamo DB

optimize the A in CAP. High availablity, low latency, tolerant to reading old values.

Leaderless system: R + W > N

Weak consistency:

* can't handle well write conflict. Can't do transaction rollback