SELECT 
  products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      products_categories.link_type = "M", 
      CONCAT(
        products_categories.category_id, 
        "M"
      ), 
      products_categories.category_id
    )
  ) AS category_ids 
FROM 
  products_categories 
  INNER JOIN categories ON categories.category_id = products_categories.category_id 
  AND categories.storefront_id IN (0, 1) 
  AND (
    categories.usergroup_ids = '' 
    OR FIND_IN_SET(0, categories.usergroup_ids) 
    OR FIND_IN_SET(1, categories.usergroup_ids)
  ) 
  AND categories.status IN ('A', 'H') 
WHERE 
  products_categories.product_id IN (
    284648, 282838, 282836, 278049, 275782, 
    272636, 269248, 266156, 265783, 266092, 
    265784, 258086, 252518, 257589, 256790, 
    256001, 252277, 242304, 239493, 237409, 
    235920, 231091, 227946, 224968, 226497, 
    225207, 225304, 225273, 204337, 201932, 
    197488, 196621, 196622, 201889, 192454, 
    193258, 192450, 108385, 144425, 175093, 
    167561, 167552, 161993, 167239, 166202, 
    165403, 165290, 164900, 164913, 161865, 
    164905, 162133, 164899, 160627, 156319, 
    132617, 139306, 120811, 139394, 132610, 
    139524, 131992, 127555, 126324, 126318, 
    126321, 108204, 114844, 120905, 108233, 
    120730, 108232, 120456, 108246, 108180
  ) 
GROUP BY 
  products_categories.product_id

Query time 0.00400

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "239.69"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "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": 435,
            "rows_produced_per_join": 435,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "43.94",
              "eval_cost": "43.50",
              "prefix_cost": "87.44",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`goimagine`.`products_categories`.`product_id` in (284648,282838,282836,278049,275782,272636,269248,266156,265783,266092,265784,258086,252518,257589,256790,256001,252277,242304,239493,237409,235920,231091,227946,224968,226497,225207,225304,225273,204337,201932,197488,196621,196622,201889,192454,193258,192450,108385,144425,175093,167561,167552,161993,167239,166202,165403,165290,164900,164913,161865,164905,162133,164899,160627,156319,132617,139306,120811,139394,132610,139524,131992,127555,126324,126318,126321,108204,114844,120905,108233,120730,108232,120456,108246,108180))"
          }
        },
        {
          "table": {
            "table_name": "categories",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "goimagine.products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 21,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "108.75",
              "eval_cost": "2.18",
              "prefix_cost": "239.69",
              "data_read_per_join": "56K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`goimagine`.`categories`.`storefront_id` in (0,1)) and ((`goimagine`.`categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`goimagine`.`categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`goimagine`.`categories`.`usergroup_ids`))) and (`goimagine`.`categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}