SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '289c6547dd2db9d2efa9d90f60645b41a960d35baedf1b802eb0032f1491afb0' 
  AND token = 'ZTTAkKhpYHpcFr2CwGfwOo0SeK19/sZ3zj+qY+EBkjQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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