SELECT 
  file_id, 
  filename, 
  filesize, 
  type 
FROM 
  cscart_cp_video_files 
WHERE 
  video_id = 2078 
  AND lang_code = 'en'

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.05"
    },
    "table": {
      "table_name": "cscart_cp_video_files",
      "access_type": "ref",
      "possible_keys": [
        "video_id"
      ],
      "key": "video_id",
      "used_key_parts": [
        "video_id",
        "lang_code"
      ],
      "key_length": "9",
      "ref": [
        "const",
        "const"
      ],
      "rows_examined_per_scan": 3,
      "rows_produced_per_join": 3,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "0.75",
        "eval_cost": "0.30",
        "prefix_cost": "1.05",
        "data_read_per_join": "3K"
      },
      "used_columns": [
        "file_id",
        "video_id",
        "lang_code",
        "filename",
        "filesize",
        "type"
      ]
    }
  }
}