# TiKV Metrics for `Slow Queries` Panel
+ Add following metrics to show the impact on TiKV layer
  + **`Process Keys`**
    + Represent the total amount of data currently accessible and transferable from the TiKV layer to the TiDB server 
  + **`Total Keys`**
    + Encompass both the data in Process Keys and the historical snapshots that must be retained according to the MVCC mechanism
![`smart`](TiDBMonitorSQLPerf07_en_001_20240125.png)
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When using the `Slow Queries` panel, it is advisable to select `Process Keys` and `Total Keys` from the `Columns` option. These metrics help us assess the amount of data an SQL query reads from TiKV.

`Process Keys` represent the total amount of data currently accessible and transferable from the TiKV layer to the TiDB server.

`Total Keys` encompass both the data in `Process Keys` and the historical snapshots that must be retained according to the `MVCC` mechanism. 

Although historical snapshots are not sent from TiKV servers to the TiDB server (except in the case of flashback queries), they are still scanned by TiKV servers during data retrieval, which results in read operations. If data is frequently modified and/or snapshot retention is set to a high value, the `Total Keys` count may significantly exceed the number of `Process Keys`.