Is it safe to perform housekeeping by deleting idempotency_key table rows that get old?

[Stouffi]

After 1 year of activity, the table idempotency_key is full of rows, more than 400K taking 2 GB space on disk.
My question as in the title: Is it safe to delete rows of this table and what would be recommended to filter those keys that are safe to be deleted?
My first intention would be to just remove them based on the created_at criteria like more than a month in the past. But should I look also to the locked_at column?