SELECT 
  product_review_id 
FROM 
  cscart_product_reviews 
  LEFT JOIN cscart_users ON cscart_product_reviews.reply_user_id = cscart_users.user_id 
  LEFT JOIN cscart_companies ON cscart_users.company_id = cscart_companies.company_id 
  LEFT JOIN cscart_country_descriptions ON cscart_product_reviews.country_code = cscart_country_descriptions.code 
  AND cscart_country_descriptions.lang_code = 'en' 
WHERE 
  1 
  AND cscart_product_reviews.product_id IN (21464, 2318) 
  AND cscart_product_reviews.status = 'A' 
GROUP BY 
  cscart_product_reviews.product_review_id

Query time 0.00201

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_product_reviews.product_review_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_reviews",
              "access_type": "range",
              "possible_keys": ["idx_product_id"],
              "key": "idx_product_id",
              "key_length": "3",
              "used_key_parts": ["product_id"],
              "rows": 21,
              "filtered": 100,
              "index_condition": "cscart_product_reviews.product_id in (21464,2318)",
              "attached_condition": "cscart_product_reviews.`status` = 'A'"
            }
          },
          {
            "table": {
              "table_name": "cscart_users",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY"],
              "key": "PRIMARY",
              "key_length": "3",
              "used_key_parts": ["user_id"],
              "ref": ["dev_db.cscart_product_reviews.reply_user_id"],
              "rows": 1,
              "filtered": 100
            }
          }
        ]
      }
    }
  }
}