# Ingest `SST` File
+ **_Before_**
  + Insert by calling **`DB::Put()`**
  + New `memtable` (`skip-list`) entry
  + Convert `memtable` into `Level 0 SST` file
  + Compaction: Move data from `Level 0` to `Level 1`, from `Level 1` to `Level 2`, ...
+ **_After_**
  + Use **`IngestFile`** feature 
  + Write all keys and values into `SST` file directly
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