SELECT 
  category_id 
FROM 
  cscart_categories 
WHERE 
  is_wallet_category = 'Y' 
  AND storefront_id = 1

Query time 0.00048

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "20.50"
    },
    "table": {
      "table_name": "cscart_categories",
      "access_type": "ALL",
      "rows_examined_per_scan": 85,
      "rows_produced_per_join": 1,
      "filtered": "1.18",
      "cost_info": {
        "read_cost": "20.30",
        "eval_cost": "0.20",
        "prefix_cost": "20.50",
        "data_read_per_join": "2K"
      },
      "used_columns": [
        "category_id",
        "storefront_id",
        "is_wallet_category"
      ],
      "attached_condition": "((`atulecarter_atul_demo8`.`cscart_categories`.`storefront_id` = 1) and (`atulecarter_atul_demo8`.`cscart_categories`.`is_wallet_category` = 'Y'))"
    }
  }
}