Nobody ever got fired for using a struct

A performance investigation at Feldera revealed that SQL tables with hundreds of nullable columns caused significant serialization overhead when mapped to Rust structs. The root issue: rkyv's ArchivedString loses Rust's niche optimization, forcing an explicit Option discriminant, and with 700+ optional fields the archived struct ballooned to 2x the in-memory size. The fix introduces a bitmap-based serialization layout that strips Option wrappers from the archived format and records nullability in a compact bitfield. A further sparse layout stores only present values with relative pointers, dramatically reducing disk I/O for wide, mostly-null rows. The customer's throughput was restored after serialized row size dropped by roughly 2x.