SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6ce051e3c143dc75d1af1473ca870562642d19aaf84e7cd739b9835dbea7ef82' 
  AND token = '2vwZV8Invjf/Y19NmsoLWSh6rbYzVlP6W8Fl7SdfbYQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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