SELECT 
  * 
FROM 
  cscart_product_bundles as bundles 
  LEFT JOIN cscart_product_bundle_descriptions as descriptions ON bundles.bundle_id = descriptions.bundle_id 
  AND descriptions.lang_code = 'vi' 
  LEFT JOIN cscart_product_bundle_product_links as links ON bundles.bundle_id = links.bundle_id 
WHERE 
  1 = 1 
  AND links.product_id = 49540 
  AND links.show_on_product_page = 'Y' 
  AND bundles.status = 'A' 
GROUP BY 
  bundles.bundle_id 
ORDER BY 
  bundles.bundle_id asc 
LIMIT 
  0, 30

Query time 0.00281

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "links",
          "access_type": "ref",
          "possible_keys": ["PRIMARY", "bundle_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "links.product_id <=> 49540 and links.show_on_product_page = 'Y'"
        }
      },
      {
        "table": {
          "table_name": "bundles",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "4",
          "used_key_parts": ["bundle_id"],
          "ref": ["dev_db.links.bundle_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "bundles.`status` = 'A'"
        }
      },
      {
        "table": {
          "table_name": "descriptions",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "10",
          "used_key_parts": ["bundle_id", "lang_code"],
          "ref": ["dev_db.links.bundle_id", "const"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(descriptions.lang_code = 'vi')"
        }
      }
    ]
  }
}