# Post locks
When you open a post someone else is editing, WordPress warns you that it is locked. Presence API keeps that lock in its own table instead of with the post, so renewing it while you edit does not slow down the rest of the site.
## How it works
```mermaid
sequenceDiagram
accTitle: A post lock stored as a presence row
accDescr: When core writes _edit_lock with update_post_meta, a filter writes the post room's _lock row and skips the meta write. When core reads the lock with get_post_meta, a filter rebuilds the time and user string from the row.
participant C as Core
participant F as Meta filters
participant T as wp_presence
C->>F: update_post_meta( _edit_lock, "time:user" )
F->>T: Write _lock in postType/{type}:{id}
F-->>C: Meta write skipped
C->>F: get_post_meta( _edit_lock )
F->>T: Read _lock
F-->>C: "time:user"
```
- `update_post_metadata`, `get_post_metadata` and `delete_post_metadata` filters write, read and remove the row, so `wp_check_post_lock()` and other callers work unchanged.
- It applies to every post type, including ones without presence support.
- The row expires after `wp_check_post_lock_window`, 150 seconds by default, as the meta lock would.
- `_lock` is reserved, so it is written even with recording off, kept at logout, and left out of reads.
- With the Post locks switch off, locks stay in post meta, as in core.
Moving locks out of post meta stops each lock refresh from bumping the posts `last_changed` value. On a synthetic large site with a Redis object cache, [#836](https://github.com/WordPress/presence-api/issues/836) measured the post query cache miss rate at about 10% with locks in post meta and about 5% with locks in `wp_presence`.
Source: [`post-lock-bridge.php`](https://github.com/WordPress/presence-api/blob/main/plugins/presence-api/includes/post-lock-bridge.php)
## Check your understanding
Recording is switched off. Do post locks still work?
Yes. `_lock` is reserved, and reserved rows are written even with recording off.