Because TiDB uses multi-version concurrency control (MVCC), when the old data is overwritten with new data, the old data is not replaced but retained along with the new data. Timestamps are used to identify the data version. Deleting data does not immediately reclaim space. Garbage collection is delayed so that concurrent transactions are able to see earlier versions of rows. This can be configured via the tidb_gc_life_time (default: 10m0s) system variable.