Protobuf is one of the most commonly used mechanism for serialization. Almost all the components / services support shaded Protobuf. Hadoop 3.1.1 , HBase 2.0.2 etc have all moved to updated Protobuf 3.x. Unfortunately Protobug 3 is not backward compatible with Protobuf 2.
Phoenix is still using protobuf-java:2.5.0 .
PHOENIX-2535 was a good step towards shading clients but excludes shading for protobuf.
It is definitely becoming very critical to upgrade protobuf as well as shade it to avoid future complexities.