SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '21184fbb750f8809c49bf8c37585945249d3c3c818687c6a9d764b5ff3a31407' 
  AND token = 'hOutwIxnsaO4FlOlGMJBLZy445PRd1CFUJLih+cVETc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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