SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '456293d5564b4ad90c5ffd173d76afcf6a3d6e040f4c0d53721cb23537e52bb4' 
  AND token = 'I6ZFdKvJyDTULVw6V34gqdWgsoEfVNPuZ+TuqBhahhA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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