SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0f0d248265cbd974479d34fc56f3522538b554402beb33fb82c879290ce3bef3' 
  AND token = '1Lt750bu16bHNG6jgmozeo2FZJl87s6NCI0XvwaCMGs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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