SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    19485, 19486, 19487, 19488, 19489, 19490, 
    19491, 19492, 19493, 19494, 19495, 
    19496, 19497, 19498, 19499, 19500
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.01043

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 (19485,19486,19487,19488,19489,19490,19491,19492,19493,19494,19495,19496,19497,19498,19499,19500) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}