# `Latch`
+ Memory lock
+ Ensure atomic within one `region`
+ Details
  + There are total `1024 x 512` `latch` slots
    +  **`config.scheduler_concurrency`**
  + Each `latch` has an `FIFO` queue for requests
  + `Latch Slot = Hash(key) % Latch Slots`
  + In a `latch`, requests of different keys do not block
![`smart`](TransactionLatch_aa_001_20221024.png)

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