Sandbox

SELECT 
  cscart_products.tracking, 
  cscart_products.amount, 
  cscart_products.min_qty, 
  cscart_products.max_qty, 
  cscart_products.qty_step, 
  cscart_products.list_qty_count, 
  cscart_product_descriptions.product 
FROM 
  cscart_products 
  LEFT JOIN cscart_product_descriptions ON cscart_product_descriptions.product_id = cscart_products.product_id 
  AND lang_code = 'fr' 
WHERE 
  cscart_products.product_id = 10141

Query time 0.00128

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	cscart_products	const	PRIMARY,product_id_idx	PRIMARY	3	const	1
1	SIMPLE	cscart_product_descriptions	const	PRIMARY,product_id	PRIMARY	9	const,const	1

Result

tracking	amount	min_qty	max_qty	qty_step	list_qty_count	product
O	1.00	0	0	0	0	Fenêtre isolantes à ouverture latérale VELUX GXL 3066