SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e9891df2a53209a999681097da4893e52b4ce881097eb84015762b930fde4b17' 
  AND token = 'K5PNthwhTCroWEoxaActvH1jD5437rEuhmT70fzOFQ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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