If you convert those PBFs to Parquet files. You can then use Duckdb to search them with sub-sec response. Plus you get the added bonus of being able to host in an S3 type cloud storage.
I also found [flatgeobuf](https://github.com/flatgeobuf/flatgeobuf), which promises something similar-ish. Perhaps not the same interface for querying, but organizing data in an r-tree format for streaming from a blob store.