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 = 266 
WHERE 
  cscart_products_categories.product_id IN (
    220173, 339556, 254330, 339744, 339676, 
    339576, 339461, 391686, 339748, 392163, 
    387088, 339667, 339645, 151062, 339684, 
    151100, 254331, 339583, 387086, 339588, 
    339708, 387055, 339826, 339454, 339547, 
    339553, 339633, 387090, 339580, 339548, 
    339657, 339777, 339632, 339649, 339711, 
    339743, 339719, 339647, 339716, 339773, 
    339776, 387065, 339474, 339756, 339745, 
    339471, 387054, 265037, 339577, 339848, 
    339666, 339552, 339665, 339669, 339767, 
    339670, 387066, 339833, 339698, 339703, 
    220171, 339557, 339544, 339646, 339651, 
    339749, 339824, 339455, 339628, 339591, 
    387052, 339784, 339549, 339565, 339673, 
    339614, 339789, 339575, 339662, 265040, 
    339595, 339834, 339853, 339653, 339658, 
    339818, 339626, 339631, 339717, 339852, 
    339559, 339470, 339545, 339487, 339542, 
    339822, 339579, 339567, 271697, 339850
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00211

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "300.76"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 107,
            "rows_produced_per_join": 107,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "22.57",
              "eval_cost": "21.40",
              "prefix_cost": "43.97",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (220173,339556,254330,339744,339676,339576,339461,391686,339748,392163,387088,339667,339645,151062,339684,151100,254331,339583,387086,339588,339708,387055,339826,339454,339547,339553,339633,387090,339580,339548,339657,339777,339632,339649,339711,339743,339719,339647,339716,339773,339776,387065,339474,339756,339745,339471,387054,265037,339577,339848,339666,339552,339665,339669,339767,339670,387066,339833,339698,339703,220171,339557,339544,339646,339651,339749,339824,339455,339628,339591,387052,339784,339549,339565,339673,339614,339789,339575,339662,265040,339595,339834,339853,339653,339658,339818,339626,339631,339717,339852,339559,339470,339545,339487,339542,339822,339579,339567,271697,339850))"
          }
        },
        {
          "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",
              "webmarco.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 107,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "107.00",
              "eval_cost": "21.40",
              "prefix_cost": "172.37",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "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": [
              "webmarco.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 5,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "107.00",
              "eval_cost": "1.07",
              "prefix_cost": "300.77",
              "data_read_per_join": "31K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`webmarco`.`cscart_categories`.`storefront_id` in (0,1)) and ((`webmarco`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`webmarco`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`webmarco`.`cscart_categories`.`usergroup_ids`)) and (`webmarco`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}