SELECT 
  cscart_vendor_plan_descriptions.*, 
  cscart_vendor_plans.* 
FROM 
  cscart_vendor_plans 
  LEFT JOIN cscart_vendor_plan_descriptions ON cscart_vendor_plan_descriptions.plan_id = cscart_vendor_plans.plan_id 
  AND cscart_vendor_plan_descriptions.lang_code = 'en' 
WHERE 
  cscart_vendor_plans.plan_id = 12 
ORDER BY 
  position asc 
LIMIT 
  0, 1

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "ordering_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_vendor_plans",
            "access_type": "const",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "plan_id"
            ],
            "key_length": "4",
            "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": "80"
            },
            "used_columns": [
              "plan_id",
              "status",
              "position",
              "is_default",
              "price",
              "periodicity",
              "commission",
              "fixed_commission",
              "products_limit",
              "revenue_limit",
              "vendor_store",
              "categories",
              "storefronts",
              "usergroups",
              "cp_is_blog_avail",
              "offer_booking",
              "ga_vendors_tracking"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_vendor_plan_descriptions",
            "access_type": "const",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "plan_id",
              "lang_code"
            ],
            "key_length": "10",
            "ref": [
              "const",
              "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": "792"
            },
            "used_columns": [
              "plan_id",
              "lang_code",
              "plan",
              "description"
            ]
          }
        }
      ]
    }
  }
}