SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21d0ea13730a3a35b4eb6320090822118acb42b8ed3f354554a5cad1b3cc16f3' 
  AND token = 'd8qWW/jptiGmP7sVnoV2YCTwbohg//EEJY9GunW1lvo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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