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 (
    430695, 430988, 430644, 431073, 431083, 
    431313, 430628, 430730, 431043, 431135, 
    430842, 430844, 431063, 431089, 431167, 
    431183, 431459, 339831, 430829, 430651, 
    430662, 430880, 430884, 431066, 430869, 
    430898, 430899, 430928, 339762, 430769, 
    430962, 431142, 339781, 430684, 431035, 
    430653, 430712, 430847, 430891, 431140, 
    430631, 430893, 430626, 431185, 381713, 
    431031, 431093, 430881, 430896, 430909, 
    431123, 339733, 339691, 430806, 430883, 
    431197, 430633, 430797, 430900, 430980, 
    431250, 339600, 430873, 431088, 431226, 
    430837, 430787, 430876, 430930, 431023, 
    430645, 430685, 430758, 430913, 431064, 
    339804, 430676, 430768, 430772, 431119, 
    431121, 339488, 430760, 430841, 430981, 
    431008, 431078, 431131, 431198, 339594, 
    430796, 430802, 430846, 431032, 431113, 
    431159, 431178, 431356, 430698, 430703
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00244

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "281.15"
    },
    "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": 100,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "21.15",
              "eval_cost": "20.00",
              "prefix_cost": "41.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (430695,430988,430644,431073,431083,431313,430628,430730,431043,431135,430842,430844,431063,431089,431167,431183,431459,339831,430829,430651,430662,430880,430884,431066,430869,430898,430899,430928,339762,430769,430962,431142,339781,430684,431035,430653,430712,430847,430891,431140,430631,430893,430626,431185,381713,431031,431093,430881,430896,430909,431123,339733,339691,430806,430883,431197,430633,430797,430900,430980,431250,339600,430873,431088,431226,430837,430787,430876,430930,431023,430645,430685,430758,430913,431064,339804,430676,430768,430772,431119,431121,339488,430760,430841,430981,431008,431078,431131,431198,339594,430796,430802,430846,431032,431113,431159,431178,431356,430698,430703))"
          }
        },
        {
          "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": 100,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "20.00",
              "prefix_cost": "161.15",
              "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": "100.00",
              "eval_cost": "1.00",
              "prefix_cost": "281.15",
              "data_read_per_join": "29K"
            },
            "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')))"
          }
        }
      ]
    }
  }
}