SELECT 
  cscart_cp_blog_posts.*, 
  cscart_cp_blog_post_descriptions.*, 
  (
    cscart_cp_blog_posts.timestamp + cscart_cp_blog_posts.post_id
  ) as next_ts, 
  (
    SELECT 
      GROUP_CONCAT(
        IF(
          cscart_cp_blog_post_categories.link_type = "M", 
          CONCAT(
            cscart_cp_blog_post_categories.category_id, 
            "M"
          ), 
          cscart_cp_blog_post_categories.category_id
        )
      )
  ) as category_ids, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path 
FROM 
  cscart_cp_blog_posts 
  LEFT JOIN cscart_cp_blog_post_descriptions ON cscart_cp_blog_posts.post_id = cscart_cp_blog_post_descriptions.post_id 
  AND cscart_cp_blog_post_descriptions.lang_code = 'ru' 
  INNER JOIN cscart_cp_blog_post_categories ON cscart_cp_blog_post_categories.post_id = cscart_cp_blog_posts.post_id 
  INNER JOIN cscart_cp_blog_categories ON cscart_cp_blog_categories.category_id = cscart_cp_blog_post_categories.category_id 
  AND cscart_cp_blog_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = cscart_cp_blog_posts.post_id 
  AND cscart_seo_names.type = 'b' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'ru' 
  AND cscart_seo_names.company_id = cscart_cp_blog_posts.company_id 
WHERE 
  cscart_cp_blog_posts.post_id = 6 
  AND cscart_cp_blog_posts.status IN ('A', 'H') 
  AND cscart_cp_blog_categories.company_id = 1 
  AND (
    cscart_cp_blog_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_cp_blog_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_cp_blog_categories.usergroup_ids
    )
  ) 
  AND (
    cscart_cp_blog_posts.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_cp_blog_posts.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_cp_blog_posts.usergroup_ids
    )
  ) 
GROUP BY 
  cscart_cp_blog_posts.post_id

Query time 0.00094

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_cp_blog_posts",
      "access_type": "const",
      "possible_keys": ["PRIMARY", "status"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["post_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_cp_blog_post_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["post_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_seo_names",
      "access_type": "const",
      "possible_keys": ["PRIMARY", "dispatch"],
      "key": "PRIMARY",
      "key_length": "210",
      "used_key_parts": [
        "object_id",
        "type",
        "dispatch",
        "lang_code",
        "company_id"
      ],
      "ref": ["const", "const", "const", "const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_cp_blog_post_categories",
      "access_type": "ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["post_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_cp_blog_categories",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "ref": ["noframes_angrybeaver.cscart_cp_blog_post_categories.category_id"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "cscart_cp_blog_categories.company_id = 1 and (cscart_cp_blog_categories.usergroup_ids = '' or find_in_set(0,cscart_cp_blog_categories.usergroup_ids) or find_in_set(1,cscart_cp_blog_categories.usergroup_ids)) and cscart_cp_blog_categories.`status` in ('A','H')"
    },
    "subqueries": [
      {
        "expression_cache": {
          "state": "uninitialized",
          "query_block": {
            "select_id": 2,
            "table": {
              "message": "No tables used"
            }
          }
        }
      }
    ]
  }
}