SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9cf3b70d2da552421afed98e899295802b7af70e466b20a09d549bc3745d350f' 
  AND token = 'UcHJtXPrpF0jW3Ojhg3mtGjNVmwo6Yz+XIDovoo0xw4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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