SELECT 
  lang.name, 
  IF(
    cscart_ult_language_values.value IS NULL, 
    lang.value, cscart_ult_language_values.value
  ) as value 
FROM 
  cscart_language_values lang 
  LEFT JOIN cscart_ult_language_values ON cscart_ult_language_values.name = lang.name 
  AND company_id = 1 
  AND cscart_ult_language_values.lang_code = lang.lang_code 
WHERE 
  lang.lang_code = 'en' 
  AND lang.name IN (
    'file_is_too_large', 'files_are_too_large', 
    'remove_this_item', 'remove_this_item', 
    'upload_another_file', 'upload_file', 
    'or', 'specify_url', 'file_is_too_large', 
    'files_are_too_large', 'remove_this_item', 
    'remove_this_item', 'upload_another_file', 
    'upload_file', 'or', 'specify_url'
  )

Query time 0.00040

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_ult_language_values",
      "access_type": "system",
      "possible_keys": ["PRIMARY"],
      "rows": 0,
      "filtered": 0,
      "const_row_not_found": true
    },
    "table": {
      "table_name": "lang",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "392",
      "used_key_parts": ["lang_code", "name"],
      "rows": 7,
      "filtered": 100,
      "attached_condition": "lang.lang_code = 'en' and lang.`name` in ('file_is_too_large','files_are_too_large','remove_this_item','remove_this_item','upload_another_file','upload_file','or','specify_url','file_is_too_large','files_are_too_large','remove_this_item','remove_this_item','upload_another_file','upload_file','or','specify_url')"
    }
  }
}

Result