SELECT 
  lang.value 
FROM 
  cscart_language_values lang 
WHERE 
  lang.lang_code = 'ru' 
  AND lang.name = 'abt__ut2.sort_by__'

Query time 0.00040

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}