Serialization

Serialization turns an in-memory object into bytes; deserialization turns the bytes back. JSON can do this, but it repeats every field name in every message and has no schema, so a renamed field breaks consumers silently.

Schema-first binary formats fix both problems. The schema is defined once, the bytes carry only values (plus small tags), and there are written rules for which schema changes are safe.

The key idea in both: the producer and the consumer upgrade at different times, so every message must be readable by both older and newer code. That property is called schema compatibility.