SELECT 
  cscart_multi_decproduct_sales.product_id, 
  amount AS sales_amount 
FROM 
  cscart_multi_decproduct_sales 
  LEFT JOIN cscart_multi_decproducts_categories ON cscart_multi_decproducts_categories.product_id = cscart_multi_decproduct_sales.product_id 
  AND cscart_multi_decproducts_categories.category_id = cscart_multi_decproduct_sales.category_id 
WHERE 
  cscart_multi_decproduct_sales.product_id IN (
    12, 148, 5, 23, 1, 149, 79, 238, 239, 172, 
    167, 8
  ) 
  AND cscart_multi_decproducts_categories.link_type = 'M'

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "19.84"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_multi_decproduct_sales",
          "access_type": "ALL",
          "possible_keys": [
            "PRIMARY",
            "pa"
          ],
          "rows_examined_per_scan": 17,
          "rows_produced_per_join": 12,
          "filtered": "70.59",
          "cost_info": {
            "read_cost": "3.04",
            "eval_cost": "2.40",
            "prefix_cost": "5.44",
            "data_read_per_join": "192"
          },
          "used_columns": [
            "category_id",
            "product_id",
            "amount"
          ],
          "attached_condition": "(`vishalecarter_multi_dec`.`cscart_multi_decproduct_sales`.`product_id` in (12,148,5,23,1,149,79,238,239,172,167,8))"
        }
      },
      {
        "table": {
          "table_name": "cscart_multi_decproducts_categories",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY",
            "link_type",
            "pt"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "category_id",
            "product_id"
          ],
          "key_length": "6",
          "ref": [
            "vishalecarter_multi_dec.cscart_multi_decproduct_sales.category_id",
            "vishalecarter_multi_dec.cscart_multi_decproduct_sales.product_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 10,
          "filtered": "91.04",
          "cost_info": {
            "read_cost": "12.00",
            "eval_cost": "2.19",
            "prefix_cost": "19.84",
            "data_read_per_join": "174"
          },
          "used_columns": [
            "product_id",
            "category_id",
            "link_type"
          ],
          "attached_condition": "(`vishalecarter_multi_dec`.`cscart_multi_decproducts_categories`.`link_type` = 'M')"
        }
      }
    ]
  }
}