SELECT 
  SQL_CALC_FOUND_ROWS cscart_cp_blog_posts.*, 
  cscart_cp_blog_post_descriptions.*, 
  cscart_cp_blog_authors.name as author_profile, 
  (
    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 
FROM 
  cscart_cp_blog_posts 
  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.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') 
  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' 
  LEFT JOIN cscart_cp_blog_authors ON cscart_cp_blog_authors.author_id = cscart_cp_blog_posts.author_id 
WHERE 
  1 
  AND cscart_cp_blog_posts.status IN ('A') 
  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
    )
  ) 
  AND (
    cscart_cp_blog_posts.use_avail_period = 'N' 
    OR (
      cscart_cp_blog_posts.use_avail_period = 'Y' 
      AND cscart_cp_blog_posts.avail_from_timestamp <= 1777807045 
      AND cscart_cp_blog_posts.avail_till_timestamp >= 1777807045
    )
  ) 
  AND (
    cscart_cp_blog_posts.timestamp + cscart_cp_blog_posts.post_id
  ) <= 1685307608 
  AND cscart_cp_blog_post_categories.category_id IN (6) 
  AND cscart_cp_blog_posts.post_id NOT IN (8) 
GROUP BY 
  cscart_cp_blog_posts.post_id 
ORDER BY 
  next_ts desc 
LIMIT 
  0, 1

Query time 0.00123

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_cp_blog_posts.`timestamp` + cscart_cp_blog_posts.post_id desc",
      "temporary_table": {
        "table": {
          "table_name": "cscart_cp_blog_authors",
          "access_type": "system",
          "possible_keys": ["PRIMARY"],
          "rows": 0,
          "filtered": 0,
          "const_row_not_found": true
        },
        "table": {
          "table_name": "cscart_cp_blog_categories",
          "access_type": "const",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["category_id"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100
        },
        "read_sorted_file": {
          "filesort": {
            "sort_key": "cscart_cp_blog_posts.post_id",
            "table": {
              "table_name": "cscart_cp_blog_posts",
              "access_type": "ALL",
              "possible_keys": ["PRIMARY", "status"],
              "rows": 23,
              "filtered": 73.91304016,
              "attached_condition": "cscart_cp_blog_posts.`status` = 'A' 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)) and (cscart_cp_blog_posts.use_avail_period = 'N' or cscart_cp_blog_posts.use_avail_period = 'Y' and cscart_cp_blog_posts.avail_from_timestamp <= 1777807045 and cscart_cp_blog_posts.avail_till_timestamp >= 1777807045) and cscart_cp_blog_posts.`timestamp` + cscart_cp_blog_posts.post_id <= 1685307608 and cscart_cp_blog_posts.post_id <> 8"
            }
          }
        },
        "table": {
          "table_name": "cscart_cp_blog_post_categories",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "6",
          "used_key_parts": ["post_id", "category_id"],
          "ref": ["noframes_angrybeaver.cscart_cp_blog_posts.post_id", "const"],
          "rows": 1,
          "filtered": 100
        },
        "table": {
          "table_name": "cscart_cp_blog_post_descriptions",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["post_id", "lang_code"],
          "ref": ["noframes_angrybeaver.cscart_cp_blog_posts.post_id", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(cscart_cp_blog_post_descriptions.lang_code = 'ru')"
        },
        "subqueries": [
          {
            "expression_cache": {
              "state": "uninitialized",
              "query_block": {
                "select_id": 2,
                "table": {
                  "message": "No tables used"
                }
              }
            }
          }
        ]
      }
    }
  }
}