SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2de8441567101b525854ff04022e625cf4deae5294bac118064f7b384b75600' 
  AND token = 'ySTi29/VXpvJNGiKh5ZJLup72eMdb3iSN/hH+KjxMJc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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