Protocol buffers (Protobuf) are a language-agnostic data serialization format developed by Google.

Low data volume: Protobuf makes use of a binary format, which is more compact than other formats such as JSON.

Persistence: Protobuf serialization is backward-compatible. This means that you can always restore previous data, even if the interfaces have changed in the meantime.

Design by contract: Protobuf requires the specification of messages using explicit identifiers and types.

Requirement for gRPC: gRPC (gRPC Remote Procedure Call) is an efficient remote procedure call system that makes use of the Protobuf format.