SELECT 
  cscart_tags.tag_id, 
  cscart_tag_links.object_id, 
  cscart_tag_links.object_type, 
  cscart_cp_tag_ext_description.tag, 
  cscart_tags.status, 
  COUNT(cscart_tag_links.tag_id) as popularity, 
  cscart_tags.categories_path, 
  cscart_tags.cp_important, 
  cscart_cp_tag_ext_description.short_name 
FROM 
  cscart_tags 
  LEFT JOIN cscart_tag_links ON cscart_tag_links.tag_id = cscart_tags.tag_id 
  LEFT JOIN cscart_cp_tag_ext_description ON cscart_tags.tag_id = cscart_cp_tag_ext_description.tag_id 
  AND cscart_cp_tag_ext_description.lang_code = 'ru' 
WHERE 
  1 
  AND cscart_tags.company_id = 1 
  AND cscart_tag_links.object_type = 'B' 
  AND cscart_tag_links.object_id = 12 
GROUP BY 
  cscart_tags.tag_id 
ORDER BY 
  cscart_tags.tag asc

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_tags.tag",
      "temporary_table": {
        "table": {
          "table_name": "cscart_tag_links",
          "access_type": "ref",
          "possible_keys": ["PRIMARY", "tag_id", "ids"],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["object_type", "object_id"],
          "ref": ["const", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "cscart_tag_links.object_type <=> 'B' and cscart_tag_links.object_id <=> 12 and cscart_tag_links.object_type = 'B'",
          "using_index": true
        },
        "table": {
          "table_name": "cscart_tags",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["tag_id"],
          "ref": ["orbit_cscart_orbit_cscart.cscart_tag_links.tag_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "cscart_tags.company_id = 1"
        },
        "table": {
          "table_name": "cscart_cp_tag_ext_description",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY", "tag_id"],
          "key": "PRIMARY",
          "key_length": "12",
          "used_key_parts": ["tag_id", "lang_code"],
          "ref": ["orbit_cscart_orbit_cscart.cscart_tag_links.tag_id", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(cscart_tag_links.tag_id = cscart_cp_tag_ext_description.tag_id and cscart_cp_tag_ext_description.lang_code = 'ru')"
        }
      }
    }
  }
}