SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    22111, 22112, 22113, 22114, 22115, 22116, 
    22117, 22118, 22119, 22120, 22121, 
    22122, 22123, 22124, 22125, 22126
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00035

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 (22111,22112,22113,22114,22115,22116,22117,22118,22119,22120,22121,22122,22123,22124,22125,22126) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}