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 = 'ro' 
  AND lang.name IN (
    'et_welcome', 'my_account', 'profile_details', 
    'downloads', 'orders', 'view_comparison_list', 
    'track_my_order', 'track_my_order', 
    'order_id', 'email', 'go', 'go', 'sign_out', 
    'sign_in', 'or', 'register', 'sign_in', 
    'et_welcome', 'my_account', 'profile_details', 
    'downloads', 'orders', 'view_comparison_list', 
    'track_my_order', 'track_my_order', 
    'order_id', 'email', 'go', 'go', 'sign_out', 
    'sign_in', 'or', 'register', 'sign_in'
  )

Query time 0.00142

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "9.81"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_ult_language_values",
          "access_type": "system",
          "possible_keys": [
            "PRIMARY"
          ],
          "rows_examined_per_scan": 0,
          "rows_produced_per_join": 1,
          "filtered": "0.00",
          "const_row_not_found": true,
          "cost_info": {
            "read_cost": "0.00",
            "eval_cost": "0.10",
            "prefix_cost": "0.00",
            "data_read_per_join": "408"
          },
          "used_columns": [
            "lang_code",
            "name",
            "value",
            "company_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "lang",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "lang_code",
            "name"
          ],
          "key_length": "392",
          "rows_examined_per_scan": 14,
          "rows_produced_per_join": 14,
          "filtered": "100.00",
          "index_condition": "((`maniamall_cscart`.`lang`.`lang_code` = 'ro') and (`maniamall_cscart`.`lang`.`name` in ('et_welcome','my_account','profile_details','downloads','orders','view_comparison_list','track_my_order','track_my_order','order_id','email','go','go','sign_out','sign_in','or','register','sign_in','et_welcome','my_account','profile_details','downloads','orders','view_comparison_list','track_my_order','track_my_order','order_id','email','go','go','sign_out','sign_in','or','register','sign_in')))",
          "cost_info": {
            "read_cost": "8.41",
            "eval_cost": "1.40",
            "prefix_cost": "9.81",
            "data_read_per_join": "5K"
          },
          "used_columns": [
            "lang_code",
            "name",
            "value"
          ]
        }
      }
    ]
  }
}

Result