SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3f9048355a06a5877e1e708b91df9a3356272f82497fc829bc586e923d4ca0ba' 
  AND token = 'U5+Tpqgf+mCDTphR9P1FxUcbVE0rq7o0MtNYnCHPmsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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