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SELECT 
  * 
FROM 
  cscart_companies AS com 
  LEFT JOIN cscart_products AS prod ON com.company_id = prod.company_id 
WHERE 
  prod.product_id = 837

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "com",
          "access_type": "system",
          "possible_keys": [
            "PRIMARY"
          ],
          "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": [
            "company_id",
            "status",
            "company",
            "lang_code",
            "address",
            "city",
            "state",
            "country",
            "zipcode",
            "email",
            "phone",
            "fax",
            "url",
            "storefront",
            "secure_storefront",
            "entry_page",
            "redirect_customer",
            "countries_list",
            "timestamp",
            "categories",
            "shippings",
            "logos",
            "commission",
            "commission_type",
            "request_user_id",
            "request_account_name",
            "request_account_data",
            "layout_id",
            "absolute_vendor_commission"
          ]
        }
      },
      {
        "table": {
          "table_name": "prod",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "product_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": [
            "product_id",
            "product_code",
            "product_type",
            "status",
            "company_id",
            "list_price",
            "amount",
            "weight",
            "length",
            "width",
            "height",
            "shipping_freight",
            "low_avail_limit",
            "timestamp",
            "updated_timestamp",
            "usergroup_ids",
            "is_edp",
            "edp_shipping",
            "unlimited_download",
            "tracking",
            "free_shipping",
            "zero_price_action",
            "is_pbp",
            "is_op",
            "is_oper",
            "is_returnable",
            "return_period",
            "avail_since",
            "out_of_stock_actions",
            "localization",
            "min_qty",
            "max_qty",
            "qty_step",
            "list_qty_count",
            "tax_ids",
            "age_verification",
            "age_limit",
            "options_type",
            "exceptions_type",
            "details_layout",
            "shipping_params",
            "buy_now_url",
            "facebook_obj_type",
            "package",
            "price_rules_options",
            "price_rule",
            "package_form",
            "cp_pp_number_of_columns",
            "show_popularity",
            "show_viewed",
            "show_added",
            "show_deleted",
            "show_bought",
            "show_total",
            "popularity_view",
            "show_popularity_header",
            "show_orders",
            "orders_view",
            "show_orders_header",
            "show_orders_items",
            "show_only_total_popularity",
            "show_only_total_orders",
            "global_popularity",
            "total_plus",
            "global_total_plus",
            "ab__stickers_manual_ids",
            "ab__stickers_generated_ids"
          ]
        }
      }
    ]
  }
}

Result

company_id	status	company	lang_code	address	city	state	country	zipcode	email	phone	fax	url	storefront	secure_storefront	entry_page	redirect_customer	countries_list	timestamp	categories	shippings	logos	commission	commission_type	request_user_id	request_account_name	request_account_data	layout_id	absolute_vendor_commission	product_id	product_code	product_type	list_price	amount	weight	length	width	height	shipping_freight	low_avail_limit	updated_timestamp	usergroup_ids	is_edp	edp_shipping	unlimited_download	tracking	free_shipping	zero_price_action	is_pbp	is_op	is_oper	is_returnable	return_period	avail_since	out_of_stock_actions	localization	min_qty	max_qty	qty_step	list_qty_count	tax_ids	age_verification	age_limit	options_type	exceptions_type	details_layout	shipping_params	buy_now_url	facebook_obj_type	package	price_rules_options	price_rule	package_form	cp_pp_number_of_columns	show_popularity	show_viewed	show_added	show_deleted	show_bought	show_total	popularity_view	show_popularity_header	show_orders	orders_view	show_orders_header	show_orders_items	show_only_total_popularity	show_only_total_orders	global_popularity	total_plus	global_total_plus	ab__stickers_manual_ids	ab__stickers_generated_ids
1	A	eshopuganda	en	Boston street	Boston	MA	US	02125	simtech@example.com	555555555	+555555555	http://example.com	eshopuganda.com	eshopuganda.com	none	Y		1439240400		1		0.00	A	0			5	0.00	837	ESFF5	P	0.00	988	0.000	0	0	0	0.00	0	1490254560	0	N	N	N	B	N	R	Y	N	N	Y	10	0	N		0	0	0	0		N	0	P	F	default	a:5:{s:16:"min_items_in_box";i:0;s:16:"max_items_in_box";i:0;s:10:"box_length";i:0;s:9:"box_width";i:0;s:10:"box_height";i:0;}			N	N	F	N	0	N	Y	Y	Y	Y	Y	L	Y	N	L	Y		Y	Y	N	0	0