APEX PDP uses AVRO library to perform JSON encoding and decoding to serialize/deserialize the data it consumes. When doing so it attempts to ensure the JSON data conforms to the AVRO Schema provided.
Optional fields are not supported in Avro. Even though, there is some support using union and default value, there is an open bug which makes it useless https://issues.apache.org/jira/browse/AVRO-2890

It would be useful to have JSON Schema Plugin support in APEX-PDP so that usecases that require optional fields in events can also use APEX-PDP. Also, the additional complexity of AVRO <--> JSON mapping can be avoided by bringing in support for JSON schema as an option.

This spike is to understand what is takes to implement a new JSON Schema plugin in APEX.