I have an Avro file of size ~1 GB. However, when I updated it to the BigQuery, it take ~5 GB for storage size. Is BigQuery storage system optimized?
BigQuery will show and charge for uncompressed data sizes.
A lot of optimizations and replication happen behind the scenes, and this is the way to keep all that simple and abstracted away. For example, loading data into BigQuery is free, and you'll get all the benefits of a well optimized and safe storage without having to invest CPU nor human hours.