SELECT 
  lang.name, 
  lang.value 
FROM 
  cscart_language_values lang 
WHERE 
  lang.lang_code = 'de' 
  AND lang.name IN (
    'availability', 'on_backorder', 'quantity', 
    'save_discount', 'save_discount', 
    'empty', 'availability', 'on_backorder', 
    'quantity', 'save_discount', 'save_discount', 
    'empty'
  )

Query time 0.00096

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.00948507,
    "nested_loop": [
      {
        "table": {
          "table_name": "lang",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "392",
          "used_key_parts": ["lang_code", "name"],
          "loops": 1,
          "rows": 5,
          "cost": 0.00948507,
          "filtered": 100,
          "attached_condition": "lang.lang_code = 'de' and lang.`name` in ('availability','on_backorder','quantity','save_discount','save_discount','empty','availability','on_backorder','quantity','save_discount','save_discount','empty')"
        }
      }
    ]
  }
}