SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 308 
WHERE 
  cscart_products_categories.product_id IN (
    2853, 2854, 2855, 2856, 2857, 2858, 2859, 
    2860, 2861, 2862, 2942, 2943, 2944, 
    2945, 2946, 2947, 2948, 2949, 2950, 
    3037, 3038, 3039, 3040, 3041, 3042, 
    3043, 3044, 3045, 3853, 5790, 5791, 
    5792, 5793, 5794, 5795, 5796, 5797, 
    5798, 6307, 6308, 6309, 6310, 6311, 
    6357, 6358, 6359, 6360, 6361, 6362, 
    6363, 6364, 6365, 6431, 6432, 6433, 
    6434, 6435, 6436, 6437, 6438, 6439, 
    6440, 6441, 6442, 6443, 6444, 6445, 
    6446, 6447, 6526, 6527, 6528, 6529, 
    6530, 6531, 6532, 6533, 6534, 6615, 
    6616, 6617, 6618, 6619, 6620, 6621, 
    6622, 2272, 2273, 2274, 2275, 2276, 
    2340, 2341, 2342, 2343, 2344
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00383

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "68.52"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.64"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 40,
            "rows_produced_per_join": 1,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "4.54",
              "eval_cost": "0.16",
              "prefix_cost": "4.70",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`gaseus`.`cscart_categories`.`storefront_id` in (0,1)) and ((`gaseus`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`gaseus`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`gaseus`.`cscart_categories`.`usergroup_ids`))) and (`gaseus`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "gaseus.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 110,
            "rows_produced_per_join": 1,
            "filtered": "0.93",
            "index_condition": "(`gaseus`.`cscart_products_categories`.`product_id` in (2853,2854,2855,2856,2857,2858,2859,2860,2861,2862,2942,2943,2944,2945,2946,2947,2948,2949,2950,3037,3038,3039,3040,3041,3042,3043,3044,3045,3853,5790,5791,5792,5793,5794,5795,5796,5797,5798,6307,6308,6309,6310,6311,6357,6358,6359,6360,6361,6362,6363,6364,6365,6431,6432,6433,6434,6435,6436,6437,6438,6439,6440,6441,6442,6443,6444,6445,6446,6447,6526,6527,6528,6529,6530,6531,6532,6533,6534,6615,6616,6617,6618,6619,6620,6621,6622,2272,2273,2274,2275,2276,2340,2341,2342,2343,2344))",
            "cost_info": {
              "read_cost": "44.00",
              "eval_cost": "0.16",
              "prefix_cost": "66.30",
              "data_read_per_join": "26"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "gaseus.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.41",
              "eval_cost": "0.16",
              "prefix_cost": "66.88",
              "data_read_per_join": "26"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}