SELECT 
  * 
FROM 
  cscart_mailing_lists 
  LEFT JOIN cscart_common_descriptions ON cscart_common_descriptions.object_id = cscart_mailing_lists.list_id 
  AND cscart_common_descriptions.object_holder = 'mailing_lists' 
  AND cscart_common_descriptions.lang_code = 'en' 
  INNER JOIN cscart_ult_objects_sharing ON (
    cscart_ult_objects_sharing.share_object_id = cscart_mailing_lists.list_id 
    AND cscart_ult_objects_sharing.share_company_id = 1 
    AND cscart_ult_objects_sharing.share_object_type = 'mailing_lists'
  ) 
WHERE 
  1 
  AND cscart_mailing_lists.status = 'A'

Query time 0.00096

JSON explain

{
  "query_block": {
    "select_id": 1,
    "const_condition": "1",
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_mailing_lists",
          "access_type": "system",
          "possible_keys": ["PRIMARY"],
          "rows": 1,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "cscart_common_descriptions",
          "access_type": "const",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "108",
          "used_key_parts": ["object_id", "lang_code", "object_holder"],
          "ref": ["const", "const", "const"],
          "rows": 1,
          "filtered": 100
        }
      },
      {
        "table": {
          "table_name": "cscart_ult_objects_sharing",
          "access_type": "const",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "159",
          "used_key_parts": [
            "share_object_id",
            "share_company_id",
            "share_object_type"
          ],
          "ref": ["const", "const", "const"],
          "rows": 1,
          "filtered": 100,
          "using_index": true
        }
      }
    ]
  }
}