Constant MAX_ON_DISK_OUTPUT_INDEX 

pub const MAX_ON_DISK_OUTPUT_INDEX: OutputIndex;

The maximum value of an on-disk serialized OutputIndex.

This allows us to store OutputLocations in 8 bytes, which makes database searches more efficient.

Consensus

This output index is impossible with the current 2 MB block size limit.

Since Zebra only stores fully verified blocks on disk, blocks with larger indexes are rejected before reaching the database.