SELECT 
  category_id 
FROM 
  cscart_categories 
WHERE 
  category_id = 266 
  AND (
    usergroup_ids = '' 
    OR FIND_IN_SET(0, usergroup_ids) 
    OR FIND_IN_SET(1, usergroup_ids)
  ) 
  AND status IN ('A', 'H') 
  AND cscart_categories.storefront_id IN (0, 1)

Query time 0.00045

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "const",
      "possible_keys": [
        "PRIMARY",
        "c_status",
        "p_category_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "category_id"
      ],
      "key_length": "3",
      "ref": [
        "const"
      ],
      "rows_examined_per_scan": 1,
      "rows_produced_per_join": 1,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "0.00",
        "eval_cost": "0.20",
        "prefix_cost": "0.00",
        "data_read_per_join": "5K"
      },
      "used_columns": [
        "category_id",
        "usergroup_ids",
        "status",
        "storefront_id"
      ]
    }
  }
}