Binary serialization and real-time compression like zstd have opened up a whole new world for me. Something like flatbuffer even lets you index into structured data without a deserialization penalty.
I’m also a fan of serialization that allows for streaming and in-memory access without fully deserializing. The project I’m working on uses CBOR and it’s been working really well. Not using the streaming, but being able to quickly access without transforming the data has been huge.