SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19917, 19918, 19919, 19920, 19921, 19922, 
    19923, 19924, 19925, 19926, 19927, 
    19928, 19929, 19930, 19931, 19932
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00913

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 (19917,19918,19919,19920,19921,19922,19923,19924,19925,19926,19927,19928,19929,19930,19931,19932) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}