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 = 'ru' 
  AND lang.name IN (
    'user_birthday', 'calendar', 'weekday_abr_0', 
    'weekday_abr_1', 'weekday_abr_2', 
    'weekday_abr_3', 'weekday_abr_4', 
    'weekday_abr_5', 'weekday_abr_6', 
    'month_name_abr_1', 'month_name_abr_2', 
    'month_name_abr_3', 'month_name_abr_4', 
    'month_name_abr_5', 'month_name_abr_6', 
    'month_name_abr_7', 'month_name_abr_8', 
    'month_name_abr_9', 'month_name_abr_10', 
    'month_name_abr_11', 'month_name_abr_12', 
    'user_birthday', 'calendar', 'weekday_abr_0', 
    'weekday_abr_1', 'weekday_abr_2', 
    'weekday_abr_3', 'weekday_abr_4', 
    'weekday_abr_5', 'weekday_abr_6', 
    'month_name_abr_1', 'month_name_abr_2', 
    'month_name_abr_3', 'month_name_abr_4', 
    'month_name_abr_5', 'month_name_abr_6', 
    'month_name_abr_7', 'month_name_abr_8', 
    'month_name_abr_9', 'month_name_abr_10', 
    'month_name_abr_11', 'month_name_abr_12'
  )

Query time 0.00107

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "22.06"
    },
    "nested_loop": [
      {
        "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": 21,
          "rows_produced_per_join": 21,
          "filtered": "100.00",
          "index_condition": "((`test_uchur_k`.`lang`.`lang_code` = 'ru') and (`test_uchur_k`.`lang`.`name` in ('user_birthday','calendar','weekday_abr_0','weekday_abr_1','weekday_abr_2','weekday_abr_3','weekday_abr_4','weekday_abr_5','weekday_abr_6','month_name_abr_1','month_name_abr_2','month_name_abr_3','month_name_abr_4','month_name_abr_5','month_name_abr_6','month_name_abr_7','month_name_abr_8','month_name_abr_9','month_name_abr_10','month_name_abr_11','month_name_abr_12','user_birthday','calendar','weekday_abr_0','weekday_abr_1','weekday_abr_2','weekday_abr_3','weekday_abr_4','weekday_abr_5','weekday_abr_6','month_name_abr_1','month_name_abr_2','month_name_abr_3','month_name_abr_4','month_name_abr_5','month_name_abr_6','month_name_abr_7','month_name_abr_8','month_name_abr_9','month_name_abr_10','month_name_abr_11','month_name_abr_12')))",
          "cost_info": {
            "read_cost": "12.61",
            "eval_cost": "2.10",
            "prefix_cost": "14.71",
            "data_read_per_join": "8K"
          },
          "used_columns": [
            "lang_code",
            "name",
            "value"
          ]
        }
      },
      {
        "table": {
          "table_name": "cscart_ult_language_values",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "lang_code",
            "name",
            "company_id"
          ],
          "key_length": "396",
          "ref": [
            "test_uchur_k.lang.lang_code",
            "test_uchur_k.lang.name",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 21,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "5.25",
            "eval_cost": "2.10",
            "prefix_cost": "22.06",
            "data_read_per_join": "8K"
          },
          "used_columns": [
            "lang_code",
            "name",
            "value",
            "company_id"
          ]
        }
      }
    ]
  }
}