SELECT 
  category_to_id 
FROM 
  cscart_ble_category_redirects 
WHERE 
  category_from_url = '/sale/clearance/primary-schoolhouse-plug-in-sconce-in-615-oil-rubbed-bronze/'

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_ble_category_redirects",
      "access_type": "ALL",
      "rows": 81,
      "filtered": 100,
      "attached_condition": "cscart_ble_category_redirects.category_from_url = '/sale/clearance/primary-schoolhouse-plug-in-sconce-in-615-oil-rubbed-bronze/'"
    }
  }
}