SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6b1f2400428c74a1786bf0c086aaf503919056e94f3c9152b6a43652f5042e0b' 
  AND token = 'xFcBVzLz0hU6WXlLJD3dzZwIqbzSl524qQcCBx33bfU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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