SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd12d63f7737ee83eb2688614a74b19ed3500a718b529f842a810ff33b0d35722' 
  AND token = 'M4vqdUDlssEadTDUV2lMcZcRYEdSflycRNp0YgHwHmk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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