SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19709, 19710, 19711, 19712, 19713, 19714, 
    19715, 19716, 19717, 19718, 19719, 
    19720, 19721, 19722, 19723, 19724
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.01132

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 (19709,19710,19711,19712,19713,19714,19715,19716,19717,19718,19719,19720,19721,19722,19723,19724) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}