SELECT 
  cscart_vendor_plan_descriptions.*, 
  cscart_vendor_plans.*, 
  manual_rating.rating AS manual_rating 
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' 
  LEFT JOIN cscart_manual_rating AS manual_rating ON manual_rating.object_id = cscart_vendor_plans.plan_id 
  AND manual_rating.object_type = 'vendor_plan' 
WHERE 
  (
    status IN('A')
  ) 
  AND (
    FIND_IN_SET(1, storefronts) 
    OR storefronts IS NULL 
    OR storefronts = ''
  ) 
ORDER BY 
  position asc

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.15"
    },
    "ordering_operation": {
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.00"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_vendor_plans",
            "access_type": "ALL",
            "rows_examined_per_scan": 2,
            "rows_produced_per_join": 1,
            "filtered": "50.00",
            "cost_info": {
              "read_cost": "0.35",
              "eval_cost": "0.10",
              "prefix_cost": "0.45",
              "data_read_per_join": "104"
            },
            "used_columns": [
              "plan_id",
              "status",
              "position",
              "is_default",
              "price",
              "periodicity",
              "commission",
              "fixed_commission",
              "products_limit",
              "revenue_limit",
              "vendor_store",
              "categories",
              "storefronts",
              "lowers_allowed_balance",
              "grace_period_to_refill_balance",
              "usergroups",
              "ga_vendors_tracking",
              "cp_is_labels_avail"
            ],
            "attached_condition": "((`nuie_scalesta_net`.`cscart_vendor_plans`.`status` = 'A') and ((0 <> find_in_set(1,`nuie_scalesta_net`.`cscart_vendor_plans`.`storefronts`)) or (`nuie_scalesta_net`.`cscart_vendor_plans`.`storefronts` is null) or (`nuie_scalesta_net`.`cscart_vendor_plans`.`storefronts` = '')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_vendor_plan_descriptions",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "plan_id",
              "lang_code"
            ],
            "key_length": "10",
            "ref": [
              "nuie_scalesta_net.cscart_vendor_plans.plan_id",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "0.10",
              "prefix_cost": "0.80",
              "data_read_per_join": "792"
            },
            "used_columns": [
              "plan_id",
              "lang_code",
              "plan",
              "description"
            ]
          }
        },
        {
          "table": {
            "table_name": "manual_rating",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "object_id",
              "object_type"
            ],
            "key_length": "102",
            "ref": [
              "nuie_scalesta_net.cscart_vendor_plans.plan_id",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "0.10",
              "prefix_cost": "1.15",
              "data_read_per_join": "112"
            },
            "used_columns": [
              "object_id",
              "object_type",
              "rating"
            ]
          }
        }
      ]
    }
  }
}