SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ff75e9333154d9a8a2c470096f4e14326ad035468d2ceb10ab45757df4471eb4' 
  AND token = 'U9i4UqFJlRbJ+FvFLtn3xIJgHvbXVovdqZsH939svYU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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