SELECT 
  * 
FROM 
  cscart_companies AS com 
  LEFT JOIN cscart_products AS prod ON com.company_id = prod.company_id 
WHERE 
  prod.product_id = 3

Query time 0.00055

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",
            "url",
            "storefront",
            "secure_storefront",
            "entry_page",
            "redirect_customer",
            "countries_list",
            "timestamp",
            "shippings",
            "logos",
            "request_user_id",
            "request_account_name",
            "request_account_data"
          ]
        }
      },
      {
        "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": "7K"
          },
          "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",
            "facebook_obj_type",
            "parent_product_id",
            "__variation_code",
            "__variation_options",
            "__is_default_variation",
            "yml2_brand",
            "yml2_origin_country",
            "yml2_store",
            "yml2_pickup",
            "yml2_delivery",
            "yml2_adult",
            "yml2_delivery_options",
            "yml2_bid",
            "yml2_cbid",
            "yml2_fee",
            "yml2_model",
            "yml2_sales_notes",
            "yml2_type_prefix",
            "yml2_offer_type",
            "yml2_market_category",
            "yml2_manufacturer_warranty",
            "yml2_expiry",
            "yml2_purchase_price",
            "yml2_description",
            "yml2_cpa",
            "buy_now_url"
          ]
        }
      }
    ]
  }
}