SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    23647, 23648, 23649, 23650, 23651, 23652, 
    23653, 23654, 23655, 23656, 23657, 
    23658, 23659, 23660, 23661, 23662
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00060

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (23647,23648,23649,23650,23651,23652,23653,23654,23655,23656,23657,23658,23659,23660,23661,23662) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}