SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dce692770cec136440fbf8a2366170e51a186d5e9cfd345bc539ae567298e46f' 
  AND token = 'RjbtfVGzjPpCS9zk7EJxnkzDoB8RzVQtMeYgezFVbqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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