There are only 180 splits. For this demo we use a file.
For more serious stuff we use postgresql.
What does the metadata structure look like?
We store the URI of each shard making up the index and, optionally, partition key and value(s). Along with a few flags, we also store the shard size, creation and last modification time. This additional metadata is not required for the query planning phase and is only useful for managing the life cycle of the shards and debugging/troubleshooting.