SELECT 
  SQL_CALC_FOUND_ROWS products.product_id, 
  products.product_type, 
  products.parent_product_id 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'de' 
  INNER JOIN cscart_products_categories as products_categories ON products_categories.product_id = products.product_id 
  INNER JOIN cscart_categories ON cscart_categories.category_id = products_categories.category_id 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
WHERE 
  1 
  AND pos_availabilty IN ('S', 'N') 
  AND cscart_categories.category_id IN (
    7, 16, 8, 9, 10, 22, 23, 24, 25, 27, 28, 39, 
    45, 67, 169, 167, 168, 182, 176, 177, 
    178, 179, 180, 183, 184, 185, 186, 187, 
    295, 349, 431, 500, 512, 551, 634
  ) 
  AND (
    products.usergroup_ids = '' 
    OR FIND_IN_SET(0, products.usergroup_ids) 
    OR FIND_IN_SET(1, products.usergroup_ids)
  ) 
  AND products.status = 'A' 
  AND products.parent_product_id = 0 
GROUP BY 
  products.product_id 
ORDER BY 
  product asc 
LIMIT 
  984, 24

Query time 0.05097

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1862.74"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": false,
        "nested_loop": [
          {
            "table": {
              "table_name": "products",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "status",
                "idx_parent_product_id"
              ],
              "key": "status",
              "used_key_parts": [
                "status"
              ],
              "key_length": "3",
              "ref": [
                "const"
              ],
              "rows_examined_per_scan": 3747,
              "rows_produced_per_join": 749,
              "filtered": "19.99",
              "cost_info": {
                "read_cost": "172.32",
                "eval_cost": "74.92",
                "prefix_cost": "547.03",
                "data_read_per_join": "3M"
              },
              "used_columns": [
                "product_id",
                "product_type",
                "status",
                "usergroup_ids",
                "parent_product_id",
                "pos_availabilty"
              ],
              "attached_condition": "((`dbggbern`.`products`.`parent_product_id` = 0) and (`dbggbern`.`products`.`pos_availabilty` in ('S','N')) and ((`dbggbern`.`products`.`usergroup_ids` = '') or (0 <> find_in_set(0,`dbggbern`.`products`.`usergroup_ids`)) or (0 <> find_in_set(1,`dbggbern`.`products`.`usergroup_ids`))))"
            }
          },
          {
            "table": {
              "table_name": "descr1",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "product_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "product_id",
                "lang_code"
              ],
              "key_length": "9",
              "ref": [
                "dbggbern.products.product_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 749,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "187.30",
                "eval_cost": "74.92",
                "prefix_cost": "809.24",
                "data_read_per_join": "2M"
              },
              "used_columns": [
                "product_id",
                "lang_code",
                "product"
              ]
            }
          },
          {
            "table": {
              "table_name": "products_categories",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "pt"
              ],
              "key": "pt",
              "used_key_parts": [
                "product_id"
              ],
              "key_length": "3",
              "ref": [
                "dbggbern.products.product_id"
              ],
              "rows_examined_per_scan": 3,
              "rows_produced_per_join": 762,
              "filtered": "33.92",
              "cost_info": {
                "read_cost": "561.89",
                "eval_cost": "76.25",
                "prefix_cost": "1595.88",
                "data_read_per_join": "11K"
              },
              "used_columns": [
                "product_id",
                "category_id"
              ],
              "attached_condition": "(`dbggbern`.`products_categories`.`category_id` in (7,16,8,9,10,22,23,24,25,27,28,39,45,67,169,167,168,182,176,177,178,179,180,183,184,185,186,187,295,349,431,500,512,551,634))"
            }
          },
          {
            "table": {
              "table_name": "cscart_categories",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "c_status",
                "p_category_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "category_id"
              ],
              "key_length": "3",
              "ref": [
                "dbggbern.products_categories.category_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 762,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "190.62",
                "eval_cost": "76.25",
                "prefix_cost": "1862.74",
                "data_read_per_join": "2M"
              },
              "used_columns": [
                "category_id",
                "usergroup_ids"
              ],
              "attached_condition": "((`dbggbern`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`dbggbern`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`dbggbern`.`cscart_categories`.`usergroup_ids`)))"
            }
          }
        ]
      }
    }
  }
}