SELECT 
  SQL_CALC_FOUND_ROWS products.product_id, 
  descr1.product as product, 
  companies.company as company_name, 
  products.product_type, 
  products.parent_product_id, 
  cscart_product_review_prepared_data.average_rating average_rating, 
  cscart_product_review_prepared_data.reviews_count product_reviews_count 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'en' 
  LEFT JOIN cscart_product_prices as prices ON prices.product_id = products.product_id 
  AND prices.lower_limit = 1 
  LEFT JOIN cscart_companies AS companies ON companies.company_id = products.company_id 
  LEFT JOIN cscart_product_review_prepared_data ON cscart_product_review_prepared_data.product_id = products.product_id 
  AND cscart_product_review_prepared_data.storefront_id = 0 
  LEFT JOIN cscart_product_popularity as popularity ON popularity.product_id = products.product_id 
WHERE 
  1 
  AND companies.status IN ('A') 
  AND products.company_id = 645 
  AND (
    products.usergroup_ids = '' 
    OR FIND_IN_SET(0, products.usergroup_ids) 
    OR FIND_IN_SET(1, products.usergroup_ids)
  ) 
  AND products.status IN ('A') 
  AND prices.usergroup_id IN (0, 0, 1) 
  AND products.company_id = 645 
  AND products.parent_product_id = 0 
GROUP BY 
  products.product_id 
ORDER BY 
  popularity.total desc, 
  products.product_id ASC 
LIMIT 
  0, 6

Query time 0.05082

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "popularity.total desc, products.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "companies",
              "access_type": "const",
              "possible_keys": ["PRIMARY"],
              "key": "PRIMARY",
              "key_length": "4",
              "used_key_parts": ["company_id"],
              "ref": ["const"],
              "rows": 1,
              "filtered": 100
            }
          },
          {
            "table": {
              "table_name": "products",
              "access_type": "index_merge",
              "possible_keys": ["PRIMARY", "status", "idx_parent_product_id"],
              "key_length": "4,3",
              "index_merge": {
                "intersect": [
                  {
                    "range": {
                      "key": "idx_parent_product_id",
                      "used_key_parts": ["parent_product_id"]
                    }
                  },
                  {
                    "range": {
                      "key": "status",
                      "used_key_parts": ["status"]
                    }
                  }
                ]
              },
              "rows": 4670,
              "filtered": 100,
              "attached_condition": "products.company_id = 645 and products.parent_product_id = 0 and (products.usergroup_ids = '' or find_in_set(0,products.usergroup_ids) or find_in_set(1,products.usergroup_ids)) and products.`status` = 'A'"
            }
          },
          {
            "table": {
              "table_name": "descr1",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY", "product_id"],
              "key": "PRIMARY",
              "key_length": "11",
              "used_key_parts": ["product_id", "lang_code"],
              "ref": ["dev_db.products.product_id", "const"],
              "rows": 1,
              "filtered": 100,
              "attached_condition": "trigcond(descr1.lang_code = 'en')"
            }
          },
          {
            "table": {
              "table_name": "cscart_product_review_prepared_data",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY"],
              "key": "PRIMARY",
              "key_length": "7",
              "used_key_parts": ["product_id", "storefront_id"],
              "ref": ["dev_db.products.product_id", "const"],
              "rows": 1,
              "filtered": 100
            }
          },
          {
            "table": {
              "table_name": "popularity",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY", "total"],
              "key": "PRIMARY",
              "key_length": "3",
              "used_key_parts": ["product_id"],
              "ref": ["dev_db.products.product_id"],
              "rows": 1,
              "filtered": 100
            }
          },
          {
            "table": {
              "table_name": "prices",
              "access_type": "ref",
              "possible_keys": [
                "usergroup",
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "key": "product_id",
              "key_length": "3",
              "used_key_parts": ["product_id"],
              "ref": ["dev_db.products.product_id"],
              "rows": 1,
              "filtered": 99.9960556,
              "attached_condition": "prices.lower_limit = 1 and prices.usergroup_id in (0,0,1)"
            }
          }
        ]
      }
    }
  }
}