SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19469, 19470, 19471, 19472, 19473, 19474, 
    19475, 19476, 19477, 19478, 19479, 
    19480, 19481, 19482, 19483, 19484
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00151

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 (19469,19470,19471,19472,19473,19474,19475,19476,19477,19478,19479,19480,19481,19482,19483,19484) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}