SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71a642ef339ee048bb56bd86738547526be732747e65a58bf70d9c278a1b7851' 
  AND token = 'lNndIU4q4PGlhFyNh5hj/1YJW1D+fvPdvijKhpQnhTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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