SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19517, 19518, 19519, 19520, 19521, 19522, 
    19523, 19524, 19525, 19526, 19527, 
    19528, 19529, 19530, 19531, 19532
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.01066

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 (19517,19518,19519,19520,19521,19522,19523,19524,19525,19526,19527,19528,19529,19530,19531,19532) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}