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1. We observed that in practice (from C3 team), although we provide overloaded function without serde, people usually just specify the serdes in each step for safety.
2. For common usage like Avro / JSON specific binding, users today need to wrap a specific serde class for each specific record class; arguably we can mitigate this problem by using some factory-like syntactic sugar like "AvroSpecificSerdeFactory.forType(Class<T>)" into the Avro serde helper class.
3. We know that due to Java type erasure, we cannot perfectly inference types from operations itself; and instead of propose a imperfect approach where "you may not need to give a serde info for some cases, and you may need to in some others", we decided to not go into that direction and bite the bullet of enforcing users to think about serdes on each stateful stage. Details of this discussion can be found here. 

This option is similar to Spark Java API. 

Alternative Option

We have once discussed and rejected another option, as to "register serdes for each class" at the top of the program via code, and only enforcing users to provide class object during the stateful operation. More specifically, users can still provide a default serde through configs, and they can "override" the serde for specific classes before defining the topology in the code, as:

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