SELECT 
  cscart_attachments.*, 
  cscart_attachment_descriptions.description 
FROM 
  cscart_attachments 
  LEFT JOIN cscart_attachment_descriptions ON cscart_attachments.attachment_id = cscart_attachment_descriptions.attachment_id 
  AND lang_code = 'en' 
WHERE 
  object_type = 'product' 
  AND object_id = 393970 
  AND type = 'M' 
  AND (
    usergroup_ids = '' 
    OR FIND_IN_SET(0, usergroup_ids) 
    OR FIND_IN_SET(1, usergroup_ids)
  ) 
  AND status = 'A' 
ORDER BY 
  position

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0051722,
    "nested_loop": [
      {
        "read_sorted_file": {
          "filesort": {
            "sort_key": "cscart_attachments.position",
            "table": {
              "table_name": "cscart_attachments",
              "access_type": "ref",
              "possible_keys": ["object_type", "type"],
              "key": "object_type",
              "key_length": "95",
              "used_key_parts": ["object_type", "object_id"],
              "ref": ["const", "const"],
              "loops": 1,
              "rows": 1,
              "cost": 0.00345856,
              "filtered": 100,
              "index_condition": "cscart_attachments.object_type = 'product'",
              "attached_condition": "cscart_attachments.object_type <=> 'product' and cscart_attachments.object_id <=> 393970 and cscart_attachments.`type` = 'M' and (cscart_attachments.usergroup_ids = '' or find_in_set(0,cscart_attachments.usergroup_ids) or find_in_set(1,cscart_attachments.usergroup_ids)) and cscart_attachments.`status` = 'A'"
            }
          }
        }
      },
      {
        "table": {
          "table_name": "cscart_attachment_descriptions",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["attachment_id", "lang_code"],
          "ref": ["u985510652_ecartify.cscart_attachments.attachment_id", "const"],
          "loops": 1,
          "rows": 1,
          "cost": 0.00171364,
          "filtered": 100,
          "attached_condition": "trigcond(cscart_attachment_descriptions.lang_code = 'en')"
        }
      }
    ]
  }
}