# `Meta` Service - `Store/Region Meta Usage`
+ `PD` generates scheduling and relocate data based on `store/region` meta information only
  + Region `leader` count on each `store` for **`balance-leader-scheduler`**
  + `Store/Region size/count` for **`balance-region-scheduler`** or **`rule-chceker`**
  + `Store/Region read/write` flow for **`balance-hot-region/leader-scheduler`**
  + ...
+ `Store/Region meta` information for client, e.g, `TiDB` knows where the data is, and where the request should send to
  + For a key like **`"b"`**, we will locate which `region (key range)` contains it and send the `read/write` request to the corresponding `region`
  + For example:
    + **`Region 1: ["", "c")`**
    + **`Region 2: ["c", "")`**
    + **`"b"`** locates in **`Region 1`** since we have **`"" < "b" < "c"`**

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