SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6cf295d07de480f7afd9a089a94528bef90702a9554870040fe4c1af95915313' 
  AND token = 'O/tlYSvWQFII6pMO352LUngm387dlamhBpviAzVAjK8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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