SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19757, 19758, 19759, 19760, 19761, 19762, 
    19763, 19764, 19765, 19766, 19767, 
    19768, 19769, 19770, 19771, 19772
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00941

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 (19757,19758,19759,19760,19761,19762,19763,19764,19765,19766,19767,19768,19769,19770,19771,19772) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}