SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f6ce5511d8fc682c433a300c769b1a6ac8c7956827f5200bc01e3eb65fd34250' 
  AND token = '854VgISwBYJK9RujhaRJ562n9qJmaJcRQIY5yosxIPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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