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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c21e01ce8d9688378ceee3ea965aa1db9040b3ac4f8e52aeec8331b1ea44e53' 
  AND token = 'GvjOfOlZMT1WlJ/V0KfD0jzvJgIWRdxp7WjRJEOxuzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}