SELECT 
  cscart_product_sales.product_id, 
  amount AS sales_amount 
FROM 
  cscart_product_sales 
  LEFT JOIN cscart_products_categories ON cscart_products_categories.product_id = cscart_product_sales.product_id 
  AND cscart_products_categories.category_id = cscart_product_sales.category_id 
WHERE 
  cscart_product_sales.product_id IN (
    10370, 10372, 10374, 10376, 10377, 10378, 
    10379, 10380, 10381, 10371, 10373, 
    10375, 12944, 15781, 12853, 12854, 
    12855, 12856, 12551
  ) 
  AND cscart_products_categories.link_type = 'M'

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_sales",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY", "pa"],
      "rows": 93,
      "filtered": 20.43010712,
      "attached_condition": "cscart_product_sales.product_id in (10370,10372,10374,10376,10377,10378,10379,10380,10381,10371,10373,10375,12944,15781,12853,12854,12855,12856,12551)"
    },
    "table": {
      "table_name": "cscart_products_categories",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY", "link_type", "pt"],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["category_id", "product_id"],
      "ref": [
        "noframes_angrybeaver.cscart_product_sales.category_id",
        "noframes_angrybeaver.cscart_product_sales.product_id"
      ],
      "rows": 1,
      "filtered": 85.05683136,
      "attached_condition": "cscart_products_categories.link_type = 'M'"
    }
  }
}