SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'db8d4dba740ffa0624d26fe54396871ebb5374f266f12b9bf02fb21546e1422f' 
  AND token = 'RtE16gO370YDnlslDGJxqPl/9BBTR392uVrLNLWBgtw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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